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Chemistry glossary (Without Definitions)[सम्पादन]

हिन्दी अंग्रेज़ी परिभाषा
A*/E low-field absorption/high-field emission with net absorptive character
ab initio from first principles
abscissa the name given to the horizontal axis in a set of two-dimensional coordinates. Commonly referred to as the x-axis.
परम ताप absolute temperature This is a temperature reading made relative to absolute zero. We use the unit of Kelvins for these readings.
परम शून्य absolute zero This is the lowest temperature possible. If you remember that temperature is a measurement of how much atoms move around in a solid, you can guess that they stop moving entirely at absolute zero. In reality, bonds still vibrate a little bit, but for the most part you don't see much happening.
absorption filter filter which allow all light through except for that in a narrow region; this is caused by the light being absorbed by the filter material.
ac arc a method of vaporization and excitation in emission spectroscopy, using voltages of less than 5000 V. Results with this method are more reproducible than that possible with a dc arc.
ac spark put a charge of 40,000V across two electrodes; the electrons which flow between them will ionize the sample.
acceleration slits positively charged ions produced in an ionization chamber of a mass spectrometer are passed into the analyzer by the accleration slits. Generally, two acceleration slits are used; one has a slight negative potential with respect to the ionization chamber in order to attract the positive ions, and the other slit has an extremely high voltage which accelerates that ions to up to half the speed of light.
शुद्धि accuracy When you measure something, the accuracy is how close your measured value is to the real value. For example, if you're actually six feet tall and your brother measures your height as six feet, one inch, he's pretty accurate. However, if your cousin measures your height as twelve feet, 13 inches, he's not accurate at all.
ACF activated carbon fibers
अम्ल acid This is anything that gives off H+ ions in water. Acids have a pH less than 7 and are good at dissolving metals. They turn litmus paper red and phenolphthalein colorless.
acid anhydride This is an oxide that forms an acid when you stick it in water. An example is SO3 - when you add water it turns into sulfuric acid, H2SO4.
acid dissociation constant (Ka) This is equal to the ratio of the concentrations of an acid's conjugate base and the acid present when a weak acid dissociates in water. That is, if you have a solution of Acid X where the concentration of the conjugate base is 0.5 M and the concentration of the acid is 10 M, the acid dissociation constant is 0.5/10 = 0.05.
activated complex In a chemical reaction, the reagents have to join together into a great big blob before they can fall back apart into the products. This great big blob is called the activated complex (a.k.a. transition state)
activation energy The minimum amount of energy needed for a chemical reaction to take place. For some reactions this is very small (it only takes a spark to make gasoline burn). For others, it's very high (when you burn magnesium, you need to hold it over a Bunsen burner for a minute or so).
activity series This is when you arrange elements in the order of how much they tend to react with water and acids.
actual yield When you do a chemical reaction, this is the amount of chemical that you actually make (i.e. The amount of stuff you can weigh).
addition reaction A reaction where atoms add to a carbon-carbon multiple bond.
adhesion the force between unlike molecules
adsorption When one substance collects of the surface of another one.
प्रश्लिष aerosols dispersions of liquids in gases and solids in gases.
afocal system where both the object and image are focused at infinity. Primarily used in magnification, or when a beam needs to be expanded but not focused.
AIMD ab inito molecular dynamics
एल्कोहल alcohol An organic molecule containing an -OH group
aldehyde An organic molecule containing a -COH group
alkali metals Group I in the periodic table.
alkaline earth metals Group II in the periodic table.
alkane An organic molecule which contains only single carbon-carbon bonds.
alkene An organic molecule containing at least one C=C bond
alkyne An organic molecule containing at least one C-C triple bond.
allomorph any of two or more crystalline forms of a substance
allotropes When you have different forms of an element in the same state. The relationship that white phosphorus and red phosphorus have to each other is that they're allotropes.
allotropic variation of physical properties without change in substance. Example: graphite, charcoal and diamond are allotropes of carbon.
मिश्रधातु alloy A mixture of two metals. Usually, you add very small amounts of a different element to make the metal stronger and harder.
ALON also known as Raytran, Al23O27N5, a glass used in IR spectroscopy
अल्फा कण alpha particle A radioactive particle equivalent to a helium nucleus (2 protons, 2 neutrons)
alpha particles the helium nucleus.
alpha-AgI A form of silver iodide which is stable at high temperatures. It acts as a superionic material, conducting electricity effectively through ionic transport. Degrades below 147 C to beta-AgI.
alpha-electron an electron in which the spin is +1/2
aluminosilicates silicates with aluminum occupying some of the silicon sites.
a-MCMB’s Activated mesocarbon microbeads. Show ferromagnetism at low temperatures
amine An organic molecule which consists of an ammonia molecule where one or more of the hydrogen atoms has been replaced by organic groups.
amino acid The basic building blocks of proteins. They're called "amino acids" because they're both amines (they contain nitrogen) and acids (carboxylic acids, to be precise)
ammeter a device that measures current
amphiprotic When something is both an acid and a base. Like amino acids, for example.
ampholyte a substance that may act as either an acid or a base
amphoteric When something is both an acid and a base. Sounds familiar, huh?
analyzer tube a part of a mass spectrometer in which positive ions are separated according to their mass/charge ratios. In TOF, this part is straight, in others, curved.
angstrom 10–10 meters.
anion photoelectron spectroscopy what you do is hit a sample with a laser and create anions. A carrier gas takes the anions down to a magnetic-bottle time-of-flight photoelectron analyzer, where you can characterize them.
anisotropy when something is not isotropic; you look at how much something is not random, and the measure of this non-randomness is the anisotropy.
annealing the tempering of glass or metals by heat. Can also be used as a treatment for thin films to give them the desired properties.
annealing point the temperature at which residual strain or stress in a glass will relieve itself in a few minutes.
annulene totally conjugated hydrocarbon
धनाग्र anode The electrode where oxidation occurs. In other words, this is where electrons are lost by a substance.
anode the electrode where oxidation occurs
antiferromagnetism where there is no net magnetic moment because the spin magnetic moments are randomly oriented, canceling them.
antinodes points of constructive interference between two waves
antireflection coating increases energy transmitted through optical surfaces by reducing Fresnel reflection losses. The criteria for such a coating are that the refractive index of the material must be equal to the square root of the substrate index when the substrate is in air; also, the phase difference between the incident wave and reflected wave must be an odd multiple of pi.
anti-Stokes fluorescence although most fluorescence complies with the Stokes law, a weak fluorescence is found at a shorter wavelength than the exciting wavelength. This additional energy is gained from excited vibrational levels within the ground state.
appearance potential the potential required to get fragmentation ions in a mass spectrometer. Generally, this value is 1-4 eV greater than the value for the ionization energy of the corresponding molecular ion.
जलीय aqueous dissolved in water
AR antireflective coating
Archimedes principle the buoyant force on a body immersed in a fluid is equal to the weight of the fluid displaced by that object.
armature where the coils of wire are mounted on an electric motor
arsenic trisulfide material used in IR windows (0.6-11 microns)
Arsenous acid H3AsO3
ASED atom superposition and electron delocalization: a method used in extended-Huckel calculations.
asphaltanes heavy polyaromatics which are insoluble in n-hydrocarbon solvents, produced in oil refineries from the vacuum distillation of virgin crude oils and processed petroleum. They form unit sheets which are arranged in stacks; the number of unit sheets which join together and the height of these sheets is strongly solvent dependant.
astigmatism when the lens is focused in one plane, but not in the plane 90 degrees to it.
atmosphere 760 torr, 101.325 kPa
atomic absorption spectroscopy (AAS) ionize a sample, and then hit the ions with light and see where absorptions take place.
atomic emission spectroscopy (AES) heat a sample and it ionizes; measure the wavelengths of the relaxations of these ions.
atomic fluorescence spectroscopy (AFS) same as AAS, but you measure the wavelengths that pass through without being absorbed.
परमाणु द्रब्यमान इकाई atomic mass unit (a.m.u.) This is the smallest unit of mass we use in chemistry, and is equivalent to 1/12 the mass of carbon-12. To all intents and purposes, protons and neutrons weigh 1 a.m.u.
परमाणू त्रिज्या atomic radius This is one half the distance between two bonded nuclei. Why don't we just measure the distance from the nucleus to the outside of the atom - after all, isn't that the same thing as a radius? It is, but atoms are also (theoretically) infinitely large (due to quantum mechanics), making this impossible to measure.
atomic solid A solid where there's a bunch of atoms in the lattice. This is different from an ionic solid, where ions are the things that are sticking together.
attenuator used in e.s.r, the attenuation of the microwave power passing along a waveguide is achieved by means of a metal plate placed along the axis of the waveguide. The degree of attenuation increases as the plate is moved away from the wall of the waveguide toward the center. In IR and UV spectroscopy, the attenuator is a toothed comb, grid, or star arrangement introduced into one beam of a spectrometer, operated either automatically through an electronic servosystem, or manually to balance the radiation in both beams.
Auer burner one source of radiation for far-IR spectroscopy. Consists of a thorium oxide mantle heated to ~2000K by a burning gas. Optimum wavelength is ~50 microns.
आफबाउ का सिद्धान्त Aufbau principle When you add protons to the nucleus to build up the elements, electrons are added into orbitals.
Auger effect the emission of a second electron after high energy radiation has expelled another.
Auger electron spectroscopy The use of the Auger effect to determine orbital energies and structure of the molecule.
autoprotolysis solvent dissociation into anion and proton.
auxochrome a saturated group with nonbonded electrons which, when attached to a chromophore, alters both the wavelength and intensity of an absorption.
अवगाद्रो का नियम Avogadro's Law If you've got two gases under the same conditions of temperature, pressure, and volume, they've got the same number of particles (atoms or molecules). This law only works for ideal gases, none of which actually exist.
azeotrope some composition of a binary mix in which the two portions cannot be separated by distillation.
b A computer program that allows people to generate accurate structures for biomolecules
background region the region of low transmission of a pass filter.
bar 100 kPa
barrier-layer cell a photoelectric detector which is made of iron coated with a semiconductor film; when light from 250-750 nm hits this cell, you get a current; this is a cell which is mainly good for intense light sources, because there is not a huge signal enhancement.
क्षार base A compound that gives off OH- ions in water. They are slippery and bitter and have a pH greater than 7.
base anhydride An oxide that forms a base when water is added. CaO is an example, turning into calcium hydroxide in water.
basis set truncation error the error you get in computational methods from not expanding an infinite series all the way to infinity. the more terms you use, the less basis set truncation error you get.
bathochromic shift shift of an absorption to a longer wavelength due to substitution or solvent effect (red shift).
बैटरी battery This is when a bunch of voltaic cells are stuck together.
Bayer process used to obtain aluminum from bauxite
BEEQ mass spectrometer a type of mass spectrometer, where the B stands for the magnetic sector, E stands for the electric sector, and Q stands for the quadropole mass filter. All of these letters stand for devices which can be used to separate the ionic products into the desired types.
bequerel SI unit of radioactivity, equal to one disintegration per second.
Bernoulli’s principle where the velocity of a fluid is high, the pressure is low, and vice-versa
beta electron an electron in which the spin is -1/2
बीटा कण beta particle A radioactive particle equivalent to an electron.
beta particle electron
bidentate ligand A ligand that can attach twice to a metal ion.
bifurcation division into two parts or branches or where these branches split apart
binary compound A compound only having two elements
बंधन उर्जा binding energy The amount of energy that holds the neutrons and protons together in the nucleus of an atom. It's a lot of energy, which is why you don't see nuclei falling apart all over the place.
BIOGRAF a computer program that allows the user to determine the positions of atoms or ions in biological molecules.
birefringence when a single incident beam is split into two refracted beams. Both of the refracted beams are parallel, with one offset from the other.
bistability when a system is able to exist in either of two steady states.
blaze wavelength the wavelength or which the angle of reflection from the groove face of a grating and the diffraction angle are the same.
BLM bilayer lipid membrane
Bohr radius the radius of the n=1 orbital in hydrogen. .529exp(-10) m.
bolometer an IR detector where changes in temperature of the responsive element due to incident radiation causes a change in conductivity of the element.
बाण्ड उर्जा bond energy The amount of energy it takes to break one mole of bonds.
बाण्ड लम्बाई bond length The average distance between the nuclei of two bonded atoms.
bonded phase chromatography (BPC) where the stationary phase of the analyte actually bonds to a solid surface; the solid surface usually consists of silica-based particles.
Born-Oppenheimer approximation nuclei are so heavy that they stay essentially stationary during the timescale of electron transfer processes
Boudouard carbon A form of carbon which is generated catalytically in the gas phase.
बायल का नियम Boyle's Law The volume of a gas at constant temperature varies inversely with pressure. In other words, if you put big pressure on something, it gets small.
Bragg equation relates the angles at which X-rays are scattered from a crystal to the spacing between the layers of molecules.
Brewster angle used in laser rod windows, at this angle light polarized in one direction passes through with very little reflection. Can be used to control the polarization of light leaving a laser. Can be calculated using tan(thetaBrewster)=n of the refractive material (where n is the refractive index).
ब्रान्स्टेट-लौरी अम्ल Bronsted-Lowry acid Acids donate protons [H+ ions] and bases grab them
Brusselators cells a theoretical system of oscillatory cells; useful because they can accurately model biological systems.
बफर buffer A liquid that resists change in pH by the addition of acid or base. It consists of a weak acid and it's conjugate base (acetic acid and sodium acetate, for example).
bulk modulus (K) defined as the ratio of hydrostatic pressure to fractional decrease in volume.
calcite calcium carbonate
उष्मामापन calorimetry The study of heat flow. Usually you'd do calorimetry to find the heat of combustion of a compound or the heat of reaction of two compounds.
capacitor a device for storing electric charge; consists of two conducting objects placed near each other but not touching; typically, when there is a voltage gradient between them, the energy can be kept stored until it needs to be discharged or until the voltage grows high enough that it spontaneously discharges.
carbon arc a carbon electrode superheated so that it emits light. Good for producing IR radiation between 10-100 microns.
carbon filament atom reservoir used in atomic spectroscopy, it enables materials to be examined without the use of highly flammable materials. When the sample is passed through a graphite tube under high voltage, it is atomized.
carboxylic acid An organic molecule with a -COOH group on it. Acetic acid is the most famous one.
carrier gas any gas used in a process which serves as a solvent for the chemical of interest. Useful in GC and other processes.
cascade process the procedure for increasing the strength of a weak signal by the progressive build-up of electron displacement in a series of dynode plates in a photomultiplier.
CASSCRF complete active space multiconfiguration self-consistent field; something that is incorporated into very complete ab initio molecular dynamics calculations.
catadiotropic systems optical systems which contain both reflecting and refracting elements; handy for correcting aberrations over wide angular fields.
उत्प्रेरक catalyst A substance that speeds up a chemical reaction without being used up by the reaction. Enzymes are catalysts because they allow the reactions that take place in the body to occur fast enough that we can live.
catenation the linking of like atoms to form chains or rings.
ऋणाग्र cathode The electrode in which reduction occurs. Reduction is when a compound gains electrons.
cathode electrode where reduction occurs
CBS complete basis set
cellulose a polysaccharide of glucose; the main component of plants.
centripetal force the force which always points from a body in rotation to the center of rotation
CESR conduction electron spin resonance
शृंखला अभिक्रिया chain reaction A reaction in which the products from one step provide the reagents for the next one. This is frequently referred to in nuclear fission (when large nuclei break apart to form smaller ones) and in free-radical reactions.
channeltron a variant of the electron multiplier; used to enhance electron signals
चार्ल का नियम Charles's Law The volume of a gas at constant pressure is directly proportional to the temperature. In other words, if you heat something up, it gets big.
CHARMM a computatinal method for simulate protein dynamics in water.
रासायनिक समीकरण chemical equation The recipe that describes what you need to do to make a reaction take place.
chemical equivalence when a nucleus or group of nuclei are related by a symmetry operation of the molecule and have the same chemical shifts.
chemical oxygen-iodine lasers (COIL) Lasers in which O2(a1deltag) generated chemically spurs the subsequent excitation of iodine atoms. Multi-kilowatt power possible.
रासायनिक गुण chemical properties Properties that can only be described by making a chemical change (by making or breaking bonds). For example, color isn't a chemical property because you don't need to change something chemically to see what color it is. Flammability, on the other hand, is a chemical property, because you can't tell if something burns unless you actually try to burn it.
chemical shift the difference in the absorption spectrum of a particular proton from the absorption position of a reference proton.
chemical vapor deposition use a vapor transport mechanism in which the gaseous reactants decompose and recombine to form some desired thin film. Decomposition and reaction are helped by having a heated substrate.
chirality When a molecule has a nonsuperimposable mirror image. To imagine this, put your hands together. Although they are mirror images, you can't put them right on top of each other so they are interchangable. Well, normal people can't, anyway.
choke coil a coil that has significant self-inductance
Christiansen filter used as a bandpass filter, these filters transmit light where the refractive index of the material matches that of the light. This wavelength changes with temperature, so when using one of these filters the temperature must be kept roughly constant.
chromatic aberration when the different wavelengths of light passing through a lens focus at different points. This effect arises from the fact that different wavelengths of light experience different refractive indexes when passing through a material.
chromatography This is when you use a system containing a mobile phase (usually a liquid in general chemistry classes) and a stationary phase (something dissolved in the liquid) to separate different compounds. This is usually done by exploiting the differing polarities of solutes, though you can do it a whole slew o' ways.
chromophore functional groups with characteristic optical absorptions or the molecules which contain them
CIDEP chemically induced dynamic electron polarization
परिपथ circuit The closed path in a circuit through which electrons flow.
circular dichroism (CD) optically active materials absorb left and right circularly polarized light to different extents.
clathrate a water cage that forms around a hydrocarbon in solution.
cloud chamber A device which is used to determine which elementary particles are being generated in a nuclear reaction. What happens is that the elementary particles go zipping through a saturated water fog, and the ionized water molecules provide nucleation centers for the condensation of water. From following these tracks, the identities of the particles can be determined.
coagulation When you destroy a colloid by letting the particles settle out.
coexistance curve a plot of density versus temperature for some substance. It measures the range over which the liquid and vapor phases can exist in equilibrium.
coherence length how long it is before waves from a light source get out of step. The less wide the spread of radiation leaving the source, the longer the coherence length.
coherent Raman beat (CRB) an ESR technique in which you monitor the electron resonance using a single, weak microwave field. The purpose is to detect coherences between nuclear transitions that are in hyperfine contact with the unpaired electron spin.
cohesion the force between like molecules
cold mirror reflects visible and transmits IR light
colligative property Any property of a solution that changes when the concentration changes. Examples are color, flavor, boiling point, melting point, and osmotic pressure.
collimated forming a highly non-divergent beam
colloid It's a suspension.
colloid when large numbers of molecules swarm together due to intermolecular forces. The dispersed phase in a colloid has a huge surface area
coma the variation of focal length with aperture.
combination bands describes weak absorptions in IR spectra corresponding to the sum of two or more fundamental vibrational frequencies. These combination modes arise from the anharmonicities of the oscillators which leads to an interaction of the vibrational states in polyatomic molecules.
ज्वलन combustion When a compound combines with oxygen gas to form water, heat, and carbon dioxide
समान आयन प्रभाव common ion effect When the equilibrium position of a process is altered by adding another compound containing one of the same ions that's in the equilibrium.
complex conjugate the imaginary portion of some function f(x)
complex ion An ion in which a central atom (usually a transition metal) is surrounded by a bunch of molecules like water or ammonia (called "ligands")
compression factor (Z) one way of determining how a gas deviates from ideality; Z=1 for ideal gases.
Compton effect the observation that X-rays scattered off of materials have a lower frequency than the incident X-rays. Attributed to collisions between the X-rays and electrons.
सांद्रता concentration A measurement of the amount of stuff (solute) dissolved in a liquid (solvent). The most common concentration unit is molarity (M), which is equal to the number of moles of solute divided by the number of liters of solution.
condensation When a vapor reforms a liquid. This is what happens on your bathroom mirror when you take a shower.
चालकता conductance A measurement of how well electricity can flow through an object.
conduction the result of collisions between molecules; when one end of an object is heated, the molecules vibrate faster and the energy is transferred to their neighbors.
युग्मी अम्ल conjugate acid The compound formed when a base gains a proton (hydrogen atom).
युग्मी क्षार conjugate base The compound formed when an acid loses a proton (hydrogen atom).
Continuous flow stirred tank reactors (CSTR) Reactors in which reagents go in, are stirred, and products come out. May also be used for other purposes, such as coupling many reaction chambers to each other in a network.
सतत स्पेक्ट्रम continuous spectrum A spectrum that gives off all the colors of light, like a rainbow. This is caused by blackbody emission.
convection when heat is transferred by the mass movement of molecules from one place to another.
copolymer when two or more monomeric units of different type are strung togther into a polymer.
coprecipitation when some precipitate contains an impurity within its bulk.
Coriolis force used in rotating body problems, it is a pseudoforce that explains why bodies at the outer edge of a rotating disk experience higher linear speeds.
corner-cube prisms also called retroreflectors, they have one corner of a cube which collects the light and returns it to the original source.
Corning 9753 calcium aluminosilicate; transmits from 0.3-4.6 microns
cornu mounting a prism system employed in spectrophotometers in which radiation is passed in through one face of the prism and out through the opposite face. The prism employed for this purpose is formed from two thirty degree quartz prisms, one of right-handed quartz and one of left-handed quartz. Produces very good dispersion but no polarization.
COSMOSIL SPYE a material used in HPLC columns. Good for separating fullerenes.
COSY correlated spectroscopy; a two-D NMR technique.
coulombic attraction the positive-negative attraction which takes place when you have two charged particles in close proximity
coulometric titration a titration method in which the current passed through the sample is used to indicate completion of the reaction.
coupling constant the separation between the peaks of a first-order multiplet produced as a result of spin-orbit coupling. The larger the value of J, the greater the coupling between the nuclei. J is usually measured in Hertz, and is not dependant on the operating frequency of the instrument.
covalent bond A chemical bond formed when two atoms share two electrons.
CPMAS NMR stands for charge polarized magic angle spinning nuclear magnetic resonance. Basically this is a method for taking molecules that have high degrees of spin and imparting some of that spin to molecules that have none. It’s handy for getting NMR signals off of atoms that usually do not have signals.
क्रान्तिक द्रब्यमान critical mass The minimum amount of radioactive material needed to undergo a nuclear chain reaction.
क्रान्तिक बिन्दु critical point The end point of the liquid-vapor line in a phase diagram. Past the critical point, you get something called a "supercritical liquid", which has weird properties.
cross-product A cross B = [A][B]sin(theta)
cryoscopic constant used to measure the freezing point depression with the addition of a solvent.
क्रिस्टल crystal A large chunk of an ionic solid.
crystal lattice see "lattice"
curie 3.7 exp10 nuclear disintegrations/sec.
Curie temperature where a ferromagnetic transition occurs
CVD chemical vapor deposition
cyclic voltammetry a method for determining the kinetics of electrode processes. Current is monitored as the potential of the electrode is changed.
डाल्टन का आंशिक दाब का सिद्धान्त Dalton's law of partial pressures The total pressure in a mixture of gases is equal to the sums of the partial pressures of all the gases put together.
damped harmonic motion when there is friction within an oscillating system, the amplitudes of the oscillation decrease over time due to this damping force.
dark current the background current that flows in photoemissive and photoconductive detectors when no radiation is falling on the detector. It is a temperature-dependant effect, and can be decreased by many orders of magnitude by operating below -20C.
dc arc put a voltage of 200-300 V across two graphite electrodes separated by about one centimeter; resulting heat causes ionization of the sample. This is commonly used in atomic absorption spectroscopy.
Debye temperature the temperature above which a certain crystal behaves classically; the temperature above which thermal vibrations are more important than quantum effects
decomposition When a big molecule falls apart to make two or more little ones.
degeneracy when one energy level corresponds to two or more states of motion. It arises when the symmetry of a molecule is such that certain fundamental frequencies are equal and is a common feature in IR spectroscopy.
degenerate Things (usually orbitals) are said to be degenerate if they have the same energy. This term is used a whole lot in quantum mechanics. Also when dealing with kids who steal cars.
deintercalation the expulsion of a foreign atom from some crystal lattice where it has been residing (usually in interstitial spaces). The opposite of intercalation.
delocalization This is when electrons can move around all over a molecule. This happens when you have double bonds on adjacent atoms in a molecule (conjugated hydrocarbon)
denature When the 3-D structure of a protein breaks down due to heat (or pH, etc), it's said to be denatured. This means that it unravels because the intermolecular forces between atoms in the chain aren't strong enough to hold it together anymore.
depolarization factor by enclosing the sample tube in polarizing sheets, each line in a Raman spectrum can be split into a horizontal component and a vertical component. The depolarization factor is the ratio of these two components.
Devarda’s alloy 50% Cu, 45% Al, 5% Zn; used to reduce inorganic nitrates and nitrites to ammonia.
dew point when air containing a given amount of water is cooled, the temperature at which the partial pressure of water equals the saturated vapor pressure.
DFT density functional theory
dialysis the separation of small solute particles from colloid particles by means of a semi-permeable membrane.
diamagnetic a diamagnetic material has no unpaired spins; when such a material without permanent dipoles has a magnetic field applied to it, the magnetic dipoles induced in the material line up opposite to that of the induced field.
diastereotopic non-interchangeable protons; the chemical shift is not ever equivalent
diathermic something that allows energy transfer as heat
विसरण diffusion When particles move from areas of high concentration to areas of low concentration. For example, if you open a bottle of ammonia on one end of the room, the concentration of ammonia molecules in the air is very high on that side of the room. As a result, they tend to migrate across the room, which explains why you can smell it after a little while. Be careful not to mix this up with effusion (see definition)
dilute-spin species when you have a species that is not very abundant; there is very little chance that there will be more than one magnetically-active isotope in a molecule.
तनुकरण dilution When you add solvent to a solution to make it less concentrated.
द्विध्रुव आघूर्ण dipole moment When a molecule has some charge separation (usually because the molecule is polar), it's said to have a dipole moment.
द्विध्रुव-द्विध्रुव बल dipole-dipole force When the positive end of a polar molecule becomes attracted to the negative end of another polar molecule.
dispersion the spreading of white light into the full spectrum
बिलयन dissociation When water dissolves a compound.
आसवन distillation This is when you separate a mixture of liquids by heating it up. The one with the lowest boiling point evaporates first, followed by the one with the next lowest boiling point, etc.
distortion departure of image shape from that predicted by first-order Gaussian optics; one example, when a rectangle is shaped like a pillow.
Doppler effect the phenomena that the frequencies of waves are blue-shifted when the source moves toward the observer and red-shifted when the source moves away from the observer.
dot product A dot B = AB cos (theta)
double-displacement reaction (a.k.a. double replacement reaction) When the cations of two ionic compounds switch places.
Dove prisms used to rotate the image in optical systems
DQ duroquinone, also known as tetramethyl-1,4-benzoquinone
drift region the length that the charged ions travel through in a TOF mass spec.
ductility how much strain a material will take before it breaks.
dynode the anodes which are used to amplify the signal in photomultiplier tubes.
E/A* low field emission/high field absorption with net absorptive character
ebullioscopic constant used to measure the boiling point elevation of a solvent with the addition of a solute
effective nuclear charge the net positive charge experienced by an electron in a many-electron atom.
effusion When a gas moves through an opening into a chamber that contains no pressure. Effusion is much faster than diffusion because there are no other gas molecules to get in the way.
effusion the rate at which a gas escapes through an orifice or hole.
EHMO extended Huckel molecular orbital
einsel lens produces focusing without an overall change in the energy of the transmitted particle. A lens used in TOF mass spec devices.
einstein the amount of energy absorbed by one mole of material undergoing a photochemical reaction
elastic deformation the linear region on a strain versus stress plot where a material will still assume its original shape.
विद्युत अपघटन electrolysis When electricity is used to break apart a chemical compound.
विद्युत अपघट्य electrolyte An ionic compound that dissolves in water to conduct electricity. Strong electrolytes break apart completely in water; weak electrolytes only fall apart a little bit. (Actually, this isn't entirely true, as Raji Heyovska informs me. Apparently strong electrolytes also dissociate partially in water, though much more so than weak ones. For more info, check out his paper at http://www.jh-inst.cas.cz/~rheyrovs. However, it is also true that the usual definition of a strong electrolyte is one that dissociates completely in water, which is why I include that definition above.)
electrolytic cell an electrochemical cell in which a non-spontaneous reaction is driven by an outside current
electron affinity The energy change that accompanies the addition of an electron to an atom in the gas phase.
electron affinity how much something wants to pick up electrons. A exothermic electron gain corresponds to a positive electron affinity.
electron gun use a controlled beam of electrons striking a surface to elevate a local area to evaporation temperature; often used in manufacture of films by vapor deposition
electron impact (EI) a commonly-used mode in a mass spec where molecules in the vapor phase are bombarded with a high-energy electron beam. These impacts are recorded as a spectrum of positive ions separated on the basis of mass/charge (m/z).
electron magnetic resonance (EMR) covers a wide range of experimets including ESE, CRB, and others in the field of ESR.
electron spin echo (ESE) a method in which you initially hit your sample, and follow that up with other pulses to generate these spin echoes. An ESR technique.
electron spin echo envelope modulation (ESEEM) a method similar to CRB, except that you typically require three pulses instead of the one required by CRB.
electron spin resonance (ESR) Also known as electron paramagnetic resonance (EPR), this method is used to determine whether radicals are formed in solution. Although it is very useful at this purpose, the sensitivity toward determination of structure is poor. It is the study of molecules containing unpaired electrons by observing the magnetic fields at which they come into resonance with monochromatic radiation. The radiation is in the microwave region, and the magnetic fields are about .3 Tesla. It can be used to study radicals generated either through chemical reactions or radiation, as well as d-metal complexes and molecules in triplet states.
electron volt corresponds to the energy acquired by an electron accelerated through a potential difference of one volt. 1eV corresponds to 1.602exp(-19)J.
electronegativity A measurement of how much an atom tends to steal electrons from atoms that it's bonded to. Elements at the top right of the periodic table (excluding the noble gases) are very electronegative while atoms in the bottom left are not very electronegative (a.k.a. "electropositive")
electroosmosis The process by which charged particles will tend to migrate toward a less charged area. Generally, when we think of this, we think of an electrolysis process where cations move in one direction, anions move in the other, and the net movement over the sample is zero. However, commonly there are areas of higher charge density, and the electroosmotic effect can greatly affect the behavior of the liquid.
electropositive When something is not at all electronegative. In fact, it tends to lose electrons rather than to gain them. Elements that are electropositive are generally to the left and bottom of the periodic table.
electrostatics the study of charges at rest
empirical formula A reduced molecular formula. If you have a molecular formula and you can reduce all of the subscripts by some constant number, the result is the empirical formula.
emulsion When very small drops of a liquid are suspended in another. An example of an emulsion is salad dressing after you've shaken it up.
emulsion dispersions of liquids in liquids, as in milk
enantiomers molecules that are nonsuperimposable mirror images of each other.
enantiotopic protons that are interchangeable through any symmetry operation (except rotation). The chemical shift is the same for these protons in an achiral environment.
ENDOR electron nuclear double resonance; an ESR technique
endothermic When a process absorbs energy (gets cold).
endpoint The point where you actually stop a titration, usually because an indicator has changed color. This is different than the "equivalence point" because the indicator might not change colors at the exact instant that the solution is neutral.
energy level A possible level of energy that an electron can have in an atom.
enthalpy A measurement of the energy content of a system.
entropy A measurement of the randomness in a system.
enzyme A biological molecule that catalyzes reactions in living creatures.
epitaxial the growth of one layer of crystals on another such that they have the same structure
equilibrium When the forward rate of a chemical reaction is the same as the reverse rate. This only takes place in reversible reactions because these are the only type of reaction in which the forward and backward reactions can both take place.
equivalence point The point in a titration at which the solution is completely neutral. This is different than the "endpoint" (see above).
escape depth the maximum depth under a surface from which ionized electrons come
ester An organic molecule with R-CO-OR' functionality.
eutectic temperature the temperature in a 2-component mixture where a liquid solution and both pure solids exist at a fixed pressure.
evanescent wave a wave on the other side of a surface from a total internal reflection; decays exponentially with distance.
even function a function in which f(x)=f(-x)
EXAFS extended X-ray absorption fine structure
excess reagent Sometimes when you do a chemical reaction, there's some of one reagent left over. That's called the excess reagent.
excimer a combination of two atoms which survives only in an excited state and which dissolves as soon as the excitation has been lost
Excimer laser A laser which is used to pump another laser, usually dye, laser.
excited state A higher energy level that electrons can jump to when energy is added.
exothermic When a process gives off energy (gets hot).
expectation value equal to the integral of (complex conjugate of psi)A(psi) d(tau). Gives the most probable value for that operator.
extensive property any property that depends on the size of the system (m, V)
extraordinary ray the beam that is deviant on being split by a birefringent crystal. It is parallel to the ordinary ray.
family The same thing as a "group" (see above)
faraday the total charge of a mole of electrons; 96,500 coulombs.
faraday cap used as a collector for the direct detection of a current of charged particles
FEP free energy perturbation
Fermi resonance the term given to accidental degeneracy arising in polyatomic molecules in which two different vibrational states accidentally possess approximately the same energy and interact with each other.
ferromagnetism when paramagnetic solids align such that the spins are oriented along the magnetic field.
first law of thermodynamics The energy of the universe is constant. It's the same thing as the Law of conservation of energy.
first law of thermodynamics the internal energy of a system is constant unless changed by doing work or heating.
संलयन fission A nuclear reaction where a big atom breaks up into little ones. This is what happens in nuclear power plants.
flame emission spectroscopy (FES) burn the sample and measure the spectral lines emitted from the elements. This method is only good for doing an elemental analysis on elements that are easily excited.
flame ionization detector when you burn the gas coming out of a GC, any organics present will be ionized. Through the use of electrodes in a detector, the current caused from the presence of these ions can be measured with high sensitivity.
flow injection analysis (FIA) when streams of reagents are mixed together and cause a chemical reaction which quickly passes into a detector; mostly handy for studying the dynamics of a reaction that happens on a microsecond timescale or more.
fluence refers to the energy density from an optical souce impingent on a sample. The higher the energy density, the higher the fluence.
fluorescence spontaneously emitted radiation which ceases immediately after exitation ceases. Comes from electonic transitions in which there is no change in multiplicity.
fluorolube a mixture of fluorinated hydrocarbons used as a mulling agent for solids in IR spectroscopy, specially formulated to obtain the spectrum in which Nujol absorption bands appear.
fluorophor any molecule in an excited state which is capable of exhibiting fluorescence.
force field a kind of calculation which is used in molecular dynamics. The calculation is semi-empirical, which means that the wavefunctions of the system are not determined.
FRAP fluorescence recovery after photobleaching
मुक्त उर्जा free energy also called "Gibbs free energy", it's the capacity of a system to do work.
free inductance decay (FID) a measure of how fast magnetic relaxations take place; an exponentially decaying sine wave with the frequency equal to the difference between the applied frequency and the resonance frequency for that nucleus.
free radical An atom or molecule with an unpaired electron. They're way reactive.
Fresnel lens an aspheric lens whose surface is broken up into many concentric annular rings. Each ring refracts incident rays to a common focus, so that a very large-aperture and small f-number thin aspheric lens results. Not to be used for precision focusing applications.
fullerene onions round fullerenes whith several layers of carbon on top of one another.
fullerenes also called buckyballs, these are an elemental form of carbon consisting of some closed surface with no degrees of unsaturation. The most well-known of these is buckminsterfullerene, C60. Related to carbon nanotubes.
functional group A generic term for a group of atoms that cause a molecule to react in a specific way. It's really common to talk about this in organic chemistry, where you have "aldehydes, carboxylic acids, amines" and so on.
G2 calculations an ab initio method for determining the entropies and enthalpies of reaction from the Schrodinger equation.
galvanic cell electrochemical cell that produces electricity spontaneously
galvanometer consists of a coil of wire suspended in the magnetic field of a permanent magnet. When current flows through this coil of wire, the magnetic field exerts a torque on the loop, which is opposed by a spring. When you attach a pointer to this coil, you get an analog readout of the current.
गामा किरण gamma ray High energy light given off during a nuclear process. When a nucleus gives off this light, it goes to a lower energy state, making it more stable.
gangue material of no value that accompanies the desired material in raw ores.
Gaussian broadening when broadening comes from the varying Doppler shifts of emitting species in a gas.
geisser tubes gas discharge tubes constructed to concentrate the discharge in a capillary tube joining two glass bulbs containing the anode and cathode. The tubes are operated by induction coils and produce intense glow discharges when small quantities of gases or vapors are contained inside the tube.
gel a semi-rigid mass of a lyophilic sol in which the dispersion medium has been absorbed by the sol molecules
GEMC the Gibbs Monte Carlo computer simulation technique; can use to simulate data on the coexisting vapor and liquid phases of a material at a given temperature.
geminate united or arranged in pairs
geodesic the shortest distance between two points on a sphere
geometrical isomer isomerism where atoms or groups of atoms can take up different positions around a double bond or a ring. This is also called cis- trans- isomerism.
g-factor a measure of how much the spin magnetic moment interacts with the local magnetic field. Used in ESR.
glass transition when a supercooled liquid becomes a glass; this is not a real phase change but represents a slowing down of the fluid relaxational motion to a point where the relaxation time is far greater than the time of observation. Not a sharp transition.
globar emits radiation from 4-15 microns. Bonded SiC rod five cm. long and 5 mm. diameter operated at 1500K. Accurately simulates a blackbody emitter.
graft terpolymers a polymer backbone onto which are grafted two series of chemically dissimilar sidechains. Depending on what these sidechains are, they can either order into periodic forms or remain microscopically mixed.
Gran plot measures the volume of acid or base or any substance to be titrated versus the volume of titrant added.
ground state The lowest energy state possible for an electron.
group A column (the things up and down) in the periodic table. Elements in the same group tend to have the same properties. These are also called "families".
अर्ध आयु half-life The time required for half of the radioactive atoms in a sample to decay. When talking about chemical reactions, it's the amount of time required to make half the reagent react.
half-reaction The oxidation or reduction part of a redox reaction.
half-wave plate a crystal that rotates the polarization of light by 90 degrees.
हैलोजन halogen The elements in group 17. They're really reactive.
उष्मा heat The kinetic energy of the particles in a system. The faster the particles move, the higher the heat.
heat of reaction The amount of heat absorbed or released in a reaction. Also called the "enthalpy of reaction"
Heisenberg uncertainty principle (deltax)(deltap)>h/2pi; (deltaE)(deltat)>h/2pi
Helmholtz coil an electromagnet wound around a charged-particle optical detector used to cancel out the effect of the earth’s magnetic field. Requires two coils.
हेस का नियम Hess's Law The enthalpy change for a change is the same whether it takes place in one big step or in many small ones.
Heterogeneous catalysis A process where you have one material supporting the actual catalyst for a reaction. One common example is where a porous inorganic material (such as a zeolite) supports small metal particles. Through using small particles, you maximize the catalyst surface area, making it more efficient.
heterogeneous mixture A mixture where the substances aren't equally distributed.
hexapole selection a method by which molecules can be oriented in space; this can be used to set the up-down symmetry.
HFCC hyperfine coupling constant
hohlraum a laboratory device to produce blackbody radiation. Consists of a closed metal tube, blackened on the inside, with a narrow slit cut into one of the flat ends. On heating the tube the radiation escaping from the slit is virtually identical with that expected from a blackbody.
HOMCOR homonuclear correlated spectroscopy; a 2-D NMR technique.
homogeneous mixture A mixture that looks really "smooth" because everything is mixed up really well.
homotopic protons that are interchangeable through an axis of symmetry. The chemical shift of these protons is the same in any environment.
hot mirror reflect IR light and transmit visible.
हुन्ड का नियम Hund's rule The most stable arrangement of electrons occurs when they're all unpaired.
HWOT half-wave optical thickness
hybrid orbital An orbital caused by the mixing of s, p, d, and f-orbitals.
hydration When a molecule has water molecules attached to it.
hydrocarbon A molecule containing carbon and hydrogen.
hydrodynamics the study of fluid in motion
hydrogen bond The tendency of the hydrogen atom stuck to an electronegative atom to become attracted to the lone pair electrons on another electronegative atom. It's a pretty strong intermolecular force, which explains why water has such a high melting and boiling point.
hydrogenation When hydrogen is added to a carbon-carbon multiple bond.
hydronium ion The H+ ion, made famous by acids.
hydroxide ion The OH- ion, made famous by bases.
hyperchromic effect an increase in absorption intensity; if structural modification leads to an increase in the molar extinction coefficient for a particular chromophoric group it is said to have brought about a hyperchromic effect.
hyperfine structure the multiplet of peaks you see in the ESR spectrum. The source of this splitting is the magnetic field arising from nuclear magnetic momets within the molecule. Generally, for molecules with a spin of I, you see 2n+1 peaks coming from the splitting. The appearance of the peaks is governed by pascal’s triangle, much like the fine structure in NMR.
hyperpolarizability the second order polarizability of a molecule. It describes how easily you can push or pull electrons around the molecule. A high hyperpolarizability is good if you want to detect second order processes like second harmonic generation.
hypochromic effect a decrease in absorption intensity.
hypsochromic shift the shift of an absorption to a shorter wavelength due to substitution or solvent effect (blue shift).
hysteresis the tendency of a magnetic substance to remain in a certain magnetic condition
Hyugen’s principle every point on a wave front can be considered as a source of tiny wavelets that spread out in the forward direction at the speed of the wave itself. The new wave front is the envelope of all these wavelets.
IAD ion-assisted deposition; used to make optical coatings at low temperatures
आदर्श गैस ideal gas A gas in which the particles are infinitely small, have a kinetic energy directly proportional to the temperature, travel in random straight lines, and don't attract or repel each other. Needless to say, there's no such thing as an ideal gas in the real world. However, we use ideal gases anyway because they make the math work out well for equations that describe how gases behave.
आदर्श गैस नियम ideal gas law PV=nRT
आदर्श विलयन ideal solution A solution in which the vapor pressure is directly proportional to the mole fraction of solvent present
IET intramolecular electron transfer
immersion lens a hemispherical lens which is used to decrease the detector size. Essentially, the image is reduced without loss of resolution.
immiscible When two substances don't dissolve in each other. Think of oil and water. They're immiscible. Organic compounds and water are frequently immiscible.
incandescence when materials are self-luminous solely owing to their high temperatures
inclusion when something is incorporated in a crystal, either in a lattice site or interstitial site.
indicator A compound that turns different colors at different pH values. We generally like to have the color change at a pH of around seven because that's where the equivalence point of a titration is.
inertia the tendency of a body to maintain its state of rest or uniform motion
infrasonic sound waves with smaller frequency than we can hear (20 Hz)
inhibitor A substance that slows down a chemical reaction.
अकार्बनिक यौगिक inorganic compound Any compound that doesn't contain carbon (except for carbon dioxide, carbon monoxide, and carbonates).
अविलेय insoluble When something doesn't dissolve.
intercalation incorporation of a foreign atom into some crystal lattice (usually in the interstitial spaces)
intermediate A molecule which exists for a short time in a chemical reaction before turning into the product.
अन्तर-आणविक बल intermolecular force A force that exists between two different molecules. Examples are hydrogen bonding (which is strong), dipole-dipole forces (which are kind of weak), and London dispersion forces (a.k.a. Van der Waal forces), which are very weak.
intrinsic semiconductor a material in which the band gap is small enough to make the material a semiconductor
Iodate ion IO3(-)
आयनिक बन्ध ionic bond A bond formed when charge particles stick together.
ionic migration A way of conducting electricity where you have charged particles moving through a matrix of some sort.
आयनन की उर्जा ionization energy The amount of energy required to pull an electron off of a gaseous atom.
iris diaphragm used in fluorimeters to control the amount of radiation from the source; consists of a series of overlapping plates arranged to move so that a roughly circular opening of variable size is produced. This is achieved by maintaining a nearly constant angle between the edges of adjacent plates.
अनुत्क्रमणीय अभिक्रिया irreversible reaction A chemical reaction in which the reagents make products but the products can't reform reagents. Most chemical reactions in basic chemistry classes are thought of as being irreversible.
Irtran 1 Magnesium fluoride
Irtran 2 zinc sulfide
isenthalpic a change that occurs without a change in enthalpy
isotherm a curve on a vol. vs. temp. vs. pressure diagram that corresponds to a single temperature
isotonic solutions Solutions containing the same osmotic pressure.
समस्थानिक isotope When an element has more than one possibility for the number of neutrons, these are called isotopes. All known elements posess isotopes. For the record, the word "isotope" doesn't imply that something is radioactive. TV told you that, and TV is stupid.
isotopomer having the same topography
isotropic medium a medium in which the waves travel at equal speed independantly of which direction they travel.
Jones reductor a metal reductor column filled with zinc
joule 1 kg sq.meter/sq. second
केल्विन Kelvin A unit used to measure temperature. One Kelvin is equal in size to one degree Celsius. To convert between degrees Celsius and Kelvins, simply add 273.15 to the temperature in degrees Celsius to get Kelvins.
Kepler’s laws of planetary motion 1) The path of each planet about the sun is an ellipse with the sun at one focus. 2) Each planet moves so that an imaginary line drawn from the sun to the planet sweeps out equal areas in equal periods of time. 3) The ratio of the squares of the periods of any two planets revolving about the sun is equal to the ratio of the cubes of their mean distances to the sun.
ketone A molecule containing a R-CO-R' functional group. Acetone (dimethyl ketone) is a common one.
गतिज उर्जा kinetic energy The energy due to the movement of an object. The more something moves, the more kinetic energy it has.
Kirchoff’s rules 1) At any junction point, the sum of the currents entering the junction must equal the sum of the currents leaving the junction. 2) The sum of the changes in potential around any closed path of a circuit must be zero.
Kjeldahl method oxidize a sample to turn nitrogen gas to ammonium ions; used to determine the amount of nitrogen in a sample.
klystron microwave generator
Knoop hardness a static measure of material hardness based on the size of impression made in the material with a pyramidal diamond indenter under specific conditions.
Kronecker delta when you take the integral over all space of a wavefunction and its complex conjugate, you get this. If it is equal to one, the wavefunctions are the same.
KRS-5 thallium bromoiodide
Lamb formula used to find the shielding constants for nuclei.
Lambertian radiator when a light emitted from a source or scattered from a surface has a radiance that is independant of viewing angle
laminar flow when the neighboring layers of a moving liquid slide by each other smoothly
Langmuir-Blodgett film lipid bilayer sorts of films. They can be made of any size and almost any thickness. They are plated on solid surfaces by taking these surfaces and dipping them into a container which has a liquid with the film floating on top.
Lanthanide contraction The tendency of the lanthanides to get small when you go from left to right in the periodic table.
Larmour frequency precessional angular velocity of an atom. Equal to the product of the magnetogyric ratio and strength of the applied magnetic field.
laser desorption mass spectrometry (LDMS) when you take a sample and hit it with a laser, you send the particles that come flying off and send them into a mass-spec.
laser threshold damage level (LDT level) the intensity at which a laser will damage a surface; coated surfaces have a lower LDT level than uncoated surfaces. My dad did a lot of research on stuff like this.
latent heats the heats of fusion and evaporation
lateral magnification the height of an image divided by the height of the object
lattice The three-dimensional arrangement of atoms or ions in a crystal.
lattice energy The energy released when one mole of a crystal is formed from gaseous ions.
lattice energy the energy required to separate completely the ions in an ionic solid.
उर्जा संरक्षण का नियम law of conservation of energy The amount of energy in the universe never changes, ever. It just changes form.
द्रब्यमान संरक्षण का नियम law of conservation of mass The amount of stuff after a chemical reaction takes place is the same as the amount of stuff you started with.
law of universal gravitation every particle attracts every other particle with a force that is proportional to the product of the masses and inversely proportional to the square of the distance between them.
LDOS local density of states
ला शैतालिए का सिद्धान्त Le Chatlier's Principle When you disturb an equilibrium (by adding more chemical, by heating it up, etc.), it will eventually go back into equilibrium under a different set of conditions.
leakage current a current that travels along an unintended path
LEED low-energy electron diffraction; can be used to investigate surface structures
length contraction the idea that the length of an object is measured to be shorter when it is moving than when it is at rest. A consequence of relativity.
Lenz’s law an induced emf always gives rise to a current whose magnetic field opposes the original change in magnetic flux.
Lewis acid An electron-pair acceptor (carbonyl groups are really good ones)
Lewis base An electron-pair donor. Things with lone pairs like water and ammonia are really good ones.
Lewis structure A structural formula that shows all of the atoms and valence electrons in a molecule.
ligand A molecule or ion that sticks to the central atom in a complex. Common examples are ammonia, carbon monoxide, or water.
light pipe a hollow cone with highly reflecting walls which collects light at one end and channels it through successive reflections to the other end. When the walls are changed to a highly absorptive material, it can be used as a light collector.
limiting reagent If you do a chemical reaction and one of the chemicals gets used up before the other one, the one that got used up is called the "limiting reagent" because it limited the amount of product that could be formed. The other one is called the excess reagent.
line spectrum A spectrum showing only certain wavelengths.
linear polarizer changes unpolarized light to polarized light.
linkage isomer isomers where a ligand differs in which atom is bonded to the metal atom.
liquid crystal a substance that has liquid-like long range disorder but some crystal-like aspects of short range order.
Littrow prism used in laser cavities to select oscillation at a particular frequency. For a particular wavelength the refracted ray on entering the prism travels normally to the exit face. The exit face is reflectively coated so that this beam travels back along the original path.
London dispersion force The forces between nonpolar atoms or molecules which is caused by momentary induced dipoles. It's real weak.
lone pair two electrons that aren't involved in chemical bonding. Also frequently referred to as an "unshared pair".
longitudinal relaxation time (T1) the time it takes after a pulse in NMR for the nuclei to get the same spin up/spin down ratio they had before the pulse. Also called spin-lattice relaxation.
longitudinal wave when the vibration of the particles in the medium move in the same direction as the motion of the wave, for example, a sound wave in air.
long-range coupling an NMR term, this describes the fact that sometimes you get spin-spin coupling between protons over distances longer than three bond lengths. This usually happens in highly conjugated systems, and the coupling constants are generally less than 3 Hz.
lyophilic solvent-attracting
lyophobic solvent-repelling
magnesia magnesium oxide
magnetic equivalence when a group of nuclei are chemically equivalent and have identical spin-spin interactions.
magnetogyric ratio this is an empirical factor with which you can find the magnetic moment of a nucleus with a non-zero magnetic moment. It cannot be calculated because there is not enough knowledge about how the nucleus works.
main-block elements Groups 1,2, and 13-18 in the periodic table. They're called main block elements because the outermost electron is in the s- or p- orbitals. What that has to do with the term "main block" is unclear to me, but hey, that's life.
masking agent a chemical added to a mixture which will block any impurity from affecting the chemical analysis; this is very handy if you have a transition metal ion which may interfere with the analysis of another transition metal ion.
द्रब्यमान mass The amount of matter in an object. The more mass, the more stuff is present.
mass defect The difference between the mass of an atom and the sum of the masses of its individual components. Atoms usually weigh a little less than if you added up the weights of all the particles. This is because that extra mass was converted into the energy which holds the atom together (see "binding energy")
Maxsorb A form of high surface area activated carbon manufactured by Kansai Coke and Chemicals, Japan.
MCT mercury-cadmium-telluride detector. Used in doing IR spectroscopy.
mean free path the average distance traveled by a gas molecule between collisions.
mechanical waves waves that travel in a material medium, such as water waves.
mechanism A step-by-step sequence that shows how the products of a reaction are made from the reagents. Mechanisms are very frequently shown during organic chemistry.
mercury arc an IR source that operates from 1-100 atmospheres. Good for producing IR radiation from 50-1400 microns.
mercury diffusion pump in this sort of device, mercury is boiled to produce a very high vacuum. The principle working here is that the heated mercury vapor is dragging the molecules of gas in the system, and getting them out of the place you are trying to maintain a high-vacuum.
mesophase a phase intermediate between liquid and solid. May also be a smectic phase.
metal reductor column a metal-filled column which is used to reduce metals in solution that are passed through it.
metallofullerenes fullerenes which contain metal atoms or ions in them. Commonly, many fullerenes are produced with metal impurities because the metal acts as a catalyst for their formation; this is especially true for nanotubes.
mica potassium aluminosilicate
microgravimetry When you go about trying to figure out the mass of something that doesn’t change much in weight. Usually you need very sensitive equipment that costs a lot.
microporous carbon A form of carbon in which you see many small pores in the surface. Generally, the micropore walls consist of graphitic crystallites, causing them to have a hydrophobic nature.
mie scattering similar to Rayleigh scattering, except that it is dependant on the shape of the particles.
Millipore filter a water purification filter which has changeable filter cartridges. Depending on how pure the water needs to be, the filter sensitivity can be changed.
mixed conductor A conductor in which both ionic migration and electrons or positive holes in the materials is responsible for current flow.
MLAR multi-layer antireflection coating
moderator a material used in a nuclear reactor to slow the neutrons; heavy water and graphite rods are two common materials.
modulus a constant which expresses a force
Mohr titration use of a chromate ion in a precipitation titration; endpoint is reached when the precipitate starts to form.
मोललता molality The number of moles of solute per kilogram of solvent in a solution. This is a unit of concentration that's not anywhere near as handy or common as molarity.
molar absorptivity represents the absorbance of a 1M solution of analyte in a 1 cm. cell; used as a constant in Beer’s Law.
मोलर द्रब्यमान molar mass The mass of one mole of particles.
मोलर आयतन molar volume The volume of one mole of a substance at STP. If you believe that everything is an ideal gas, this is always 22.4 liters. Unfortunately, there's no such thing as an ideal gas.
मोलरता molarity A unit of concentration equal to moles of solute divided by liters of solution.
मोल mole 6.02 x 1023 things.
mole fraction The number of moles of stuff in a mixture that are due to one of the compouds.
mole ratio The ratio of moles of what you've been given in a reaction to what you want to find. Handy in stoichiometry.
molecular beams a narrow stream of molecules which is directed toward other molecules
आणविक यौगिक molecular compound A compound held together by covalent bonds.
molecular dynamics (MD) A way of figuring out how molecules will behave through the use of quantum mechanical methods. Different in form and method from semi-empirical methods such as the Monte Carlo method.
आणविक सूत्र molecular formula A formula that shows the correct quantity of all of the atoms in a molecule.
monatomic ion An ion that has only one atom, like the chloride ion.
monochromator light goes in, hits a dispersing element (such as a diffraction grating or prism) and some portion of light is allowed out the other side.
monodisperse when a polymer has only one molecular mass. They are typically generated by natural processes.
Monte Carlo method a semi-empirical method for determining molecular dynamics of a system. What you do is to move the particles via a random method. Whether or not this new configuration is accepted depends on 1) If the PE is not greater than before the change, it is accepted. 2) If it is accepted, it is accepted in proportion to how much the potential change is for all the particles in the system.
MOST Korean Ministry of Science and Technology
mull a finely ground powder dispersed in an oil for IR spectroscopy.
multimeter a device that can measure voltage, current and resistance; may also be called a volt-ohm-meter (VOM)
multiplicity Equal to 2S+1
nanotube A long cylindrical structure related to the fullerenes. The structure of these rods appears to be a stacked graphite ring structure on the outside, and a randomized graphitic crystal structure on the inside. Generally, these tubes form best at temperatures above 1200C, and not at all under 200C.
nascent beginning to develop, immature.
Nd AG laser: A laser with a Nd/Yttrium aluminum garnet rod.
nebulizer a way of producing an aerosol for AAS.
Neel temperature where anti-ferromagnetic transitions occur
Nernst glower produces IR light to 15 microns. A hollow rod about three centimeters long and one millimeter diameter made from ZrO2 and Y2O3 mixed with CeO2 or ThO2. Operated at temperatures from 1500-2000K.
Nernst heat theorem entropy change of a transformation approaches zero as the temperature approaches zero
neutralization reaction The reaction of an acid with a base to form water and a salt.
neutrino a particle with no charge or mass that is given off during beta decay
newton kg m/second squared; unit of force
Newton’s rings when a curved glass surface is placed in contact with a flat glass surface, a series of concentric rings is observed when illuminated from above with monochromatic light. This is caused by the reflection of light from the surfaces, giving constructive and destructive interference. This phenomena can be used to test whether or not a lens is properly ground.
NIST National Institute of Standards and Technology
node A location in an orbital where there's no probability of finding an electron.
nodes points of destructive interference between two waves.
nonconservative field describes the electric field produced by a changing magnetic field.
nonpolar covalent bond A covalent bond where the electrons are shared equally between the two atoms.
normal boiling point The boiling point of a substance at 1.00 atm.
normal melting point The melting point of a substance at 1.00 atm.
नार्मलता normality The number of equivalents of a substance dissolved in a liter of solution.
n-type semiconductor donor band that is full donates to another empty band, giving rise to conductivity
नाभिकीय संलयन nuclar fusion When many small atoms combine to form a large one. This occurs during a thermonuclear reaction.
nuclear fission This is when the nucleus of an atom breaks into many parts.
nuclear quadrupole coupling constant a molecular parameter which provides a sensitive probe of electronic and surrounding molecular structure near some quadrupolar nucleus of interest.
नाभिकीय अभिक्रिया nuclear reaction Any reaction that involves a change in the nucleus of an atom. Nuclear reactions take loads of energy, which is why you don't see them much around the lab.
nucleation when a small particle or molecule spurs the condensation of a vapor or solid. Can occur with solid or liquid particles, or even ions.
nucleon A particle (such as proton or neutron) that's in the nucleus of an atom.
nujol a high-boiling petroleum oil often used as a solvent for IR spectroscopy because it is relatively free of IR absorption bands.
observable a physically-measurable property of a system
occlusion when a impurity is “surrounded” by the material of interest, but not actually incorporated into the crystal lattice.
अष्टक नियम octet rule All atoms want to be like the nearest noble gas. (Well, they all want to have the same number of valence electrons, anyway). To do this, they either gain or lose electrons (to form ionic compounds) or share electrons (to form covalent compounds).
odd b if g(-x)=-g(x), then g is an odd function.
off-axis chromatic aberration when chromatic aberration results in a difference in image size.
Ohm’s law V=I/R (voltage equals current/resistance)
operator a rule that transforms a given function into another function
Opperman source an IR source that consists of a ceramic tube with an internal noble metal heater. It requires no preheating.
optic axis the direction in a birefringent crystal along which no splitting of the beam occurs
प्रकाशीय समावयवता optical isomerism Isomerism in which the isomers cause plane polarized light to rotate in different directions.
orbital This is where the electrons in an atom live.
ordinary ray the beam that does not deviate upon being split by a birefringent crystal
कार्बनिक यौगिक organic compound A compound that contains carbon (except carbon dioxide, carbon monoxide, and carbonates)
परासरण osmosis The flow of a pure liquid into an area of high concentration through a semi-permeable membrane.
Ostwald process a catalytic process which is used to make nitric acid from ammonia.
Ostwald ripening coarsening in crystal structures; it is an inherent property of crystals at a solid-liquid interface. The coarsening and enarging of crystals at surfaces is driven by a thermodynamic driving force to reduce the surface to volume ratio; this in turn lowers the interfacial or line energy.
आक्सीकरण oxidation When a substance loses electrons.
आक्सीकरण संख्या oxidation number The apparent charge on an atom.
oxygen-free high-conductivity copper (OFHC) a form of copper used frequently for instrument applications because of high purity, good conductivity and resistance to hydrogen embrittlement.
PAH polyaromatic hydrocarbon
paramagnetic a paramagnetic material has unpaired electrons; when such a material which has molecules with permanent dipole moments is placed in an external field, they orient themselves. When there is no field, the molecules are randomly oriented.
parity operator replaces each cartesian coordinate with its negative
parrafins normal alkanes with no functionality and no branching.
आंशिक दाब partial pressure The pressure of one gas in a mixture. For example, if you had a 50:50 mix of helium and hydrogen gases and the total pressure was 2 atm, the partial pressure of hydrogen would be 1 atm.
pascal newton/sq. meter
Pascal’s triangle the diagram that gives the peak intensity ratios for NMR and ESR. It does have the appearance of a triangle, and each row has numbers which correspond to the sum of the numbers on top of it.
passband the primary wavelength interval of transmission of a gas filter.
पाली का अपवर्जन का सिद्धान्त Pauli exclusion principle No two electrons in an atom can have the same quantum numbers.
pellicles beam-splitting mirrors made of high-tensile-strength polymer stretched over a flat metal surface
pencil angle a half angle which describes the rays emanating from a point at the edge of an object
Penta prisms deviate a ray of light by 90 degrees without inversion or reversion. Called penta prisms because they are pentagonal solids.
percent yield The actual yield divided by the theoretical yield, times 100.
आवर्त काल period A row (left to right) in the periodic table.
आवर्तता का नियम periodic law The properties of elements change with increasing atomic number in a periodic way. That's why you can stick the elements into a big chart and have the elements line up in nice families.
PES potential energy surface
पीएच pH -log[H+]
फेज phase The state of a compound (solid, liquid, or gas)
फेज आरेख phase diagram A chart which shows how the phase depends on various conditions of temperature and pressure.
phase velocity the velocity at which the crests of a wave move.
phonon a lattice vibration
phosphorescence spontaneous emission persists for a long time after the exciting radiation ceases. This long-lived relaxation arises from the fact that the transition being made here is a forbidden inter-system crossing.
photoconductive detector a change in number of incident photons causes a fluctuation in the number of free charge carriers in a semiconductor. Electrical conductivity is inversely proportional to the number of incident photons.
photoelastic effect sensitivity of the optical dielectric response to changes in density.
photoelectric effect ejection of electrons from metals when exposed to UV radiation.
photoelectron spectroscopy (PES) measures the ionization energies of molecules when electrons are ejected from different orbitals; it uses these to infer the orbital energies. UV photoelectron spectroscopy is for hitting more energetic molecules, and X-Ray photoelectron spectroscopy is handy for pulling off the core electrons.
photomultiplier tube (PMT) when light comes in, it hits an anode surface that releases many electrons. When nine of these are placed in series, there is a huge increase in the original signal. The anode surfaces are called dynodes.
photosensitized reaction when the reagent is not actually what absorbs light; instead, a photosensitizer picks up light and transfers the energy to the reagents.
photovoltaic detector a change in the number of photons incident of a p-n junction causes fluctuations in the voltage generated by the junction.
भौतिक गुण physical property A property which can be determined without changing something chemically. If that doesn't make sense, see the definition of "chemical change".
physical vapor deposition (PVD) get a source material into the vapor phase and then allow the molecules to condense on the surface of a thin film
पाई बन्ध pi-bond A double bond.
piezoelectric effect the phenomenon in which a crystal under the action of a mechanical stress becomes electrically charged, with opposite charges at the two ends of the crystal. Does not occur in centrosymmetric crystals, except for those in the cubic 432 group.
plastic deformation the strain at which a solid can no longer regain its original shape.
Pockel’s cell an optical phase modulator
Poise the cgs unit of viscosity; equal to dyne*sec/centimeters squared
polar covalent bond A covalent bond where one atom tries to grab the electrons from the other one. This occurs because the electronegativities of the two atoms aren't the same.
polyampholyte when a macromolecule has mixed anion and cation character.
बहुपरमाणवीय polyatomic contains more than one atom.
polydisperse When a polymer exists over a wide range of molecular masses; characteristic of man-made polymeric materials.
polymer A molecule containing many repeating units. Plastics are polymers and are formed by free radical chain reactions.
polymorph the varying structures of solid materials when the temperature is changed
polyprotic acid An acid that can give up more than one hydronium ion. Examples are sulfuric acid and phosphoric acid.
स्थितिज उर्जा potential energy The energy something has because of where it is. Things that are way up high have more potential energy than things that are way down low because they have farther to fall.
Poynting vector the energy an EM wave transports per unit time per unit area. Denoted as the vector S.
precision A measurement of how repeatable a measurement is. The more significant figures, the more precise the measurement.
दाब pressure Force/area
pressure amplitude represents the maximum and minimum amounts by which the pressure varies from normal ambient pressure. Usually used in describing shock waves or sound waves.
primary creep when you put strain on a substance, this is the movement that is still recoverable.
उत्पाद product The thing you make in a chemical reaction.
proton decoupling when you are doing C-NMR, you have the possibility that the spins of the carbon and that of the protons will couple, and the spectrum would then be very hard to understand. In this method, you get rid of any coupling by following the initial pulse with a pulse that randomizes the spins of the protons; in this way, the signal averaging gets rid of any spin coupling between them. It does make it easier to see how many carbons there are, although it makes it impossible to integrate peak heights to figure out the abundances of each equivalent carbon.
p-type semiconductor low-lying acceptor band gives rise to conductivity
pulsed gradient spin echo (PSGE) An NMR technique which is used to study the speed of liquid motion.
pyranose a six-membered ring sugar molecule.
pyrolytic breaking apart through heat
pyromagnetic when you can change magnetic properties of a compound through heating
quadrupole a “double dipole”; a molecule with a quadrupole will have no dipole moment because the two dipoles present in the molecule cancel each other out. A good example is carbon dioxide.
quadrupole mass filter used in mass spec, this tool has four voltage-carrying rods which serve to give ions which travel between them oscillations. Only ions with the right mass/charge ratio (m/z) can undergo these oscillations without hitting one of these rods.
quantum number 1) n is the principal quantum number. n has possible values of 1,2,3... 2) l is the orbital quantum number, having values of 0....n-1 3) ml is the magnetic quantum number, having values of -l, -l+1....l 4) ms is the spin quantum number, having a value of either 1/2 or -1/2.
क्वान्टम सिद्धान्त quantum theory The branch of physical chemistry that describes how energy can only exist at certain levels and makes generalizations about how atoms behave from this assumption.
quarter wave plate used to change linearly polarized light to circularly polarized light
Q-value the total energy released by the radioactive disintegration of a nucleus
QWOT quarter-wave optical thickness
radiant power total amount of energy emitted by a light source per second
रेडियो सक्रिय radioactive When a substance has an unstable nucleus that can fall apart, it's referred to as radioactive.
राउल्ट का नियम Raoult's Law The vapor pressure of a solution is directly proportional to the mole fraction of the solvent.
rate determining step The slowest step in a chemical reaction.
rate law A mathematical expression for the speed of a reaction as a function of concentration. A hint: It's usually true that things go faster if you have more stuff in the first place.
Rayleigh scattering when light is scattered by particles much smaller than the wavelength. The shorter the wavelength, the more intense the scattering.
RC circuit a circuit that uses both resistors and capacitors
reactive plasma deposition (RPD) similar to CVD, except that an rf plasma helps the decomposition/recombination process of the reactants.
rectifier a device that turns ac power into dc power
redox reaction A reaction that has both an oxidation and reduction.
reduced mass =m1m2(m1+m2)
refractory metals include tungsten, tantalum and molybdenum; used for electrode materials because they have a low, uniform surface potential, do not oxidize, and are bakeable
relativity principle the basic laws of physics are the same in all inertial reference frames
relaxation times consist of T1 (longitudinal relaxation time) and T2 (transverse relaxation time). Basically, the relaxation times correspond to the time it takes after the pulse in NMR or other spectroscopic tecniques for the molecules to go back to their Boltzmann distribution of states.
REMPI resonance enhanced multi-photon ionization
resistance thermometer uses the dependance of electrical resistance on temperature to measure the temperature.
resolution (of a lens) the ability of a lens to produce distinct images of two point objects very close together
resonance what happens when you have two or more oscillators connected in some way; these oscillators tend to get the same frequency because this gives more efficient energy transfer between them. This coupling of frequencies is resonance.
resonance structure When more than one valid Lewis structure can be drawn for a molecule, these structures are said to be resonance structures. Resonance structures arise from the fact that the electrons are delocalized.
resonant two-photon ionization (R2PI) A process in which two photons strike a sample and ionize the molecules. One good thing about this process is that the product ions generally have known structure.
rest mass the mass of an object as measured in a reference frame where it is at rest.
Reststrahlen filter utilizes the phenomena that reflections of white light from crystal surfaces will contain only one region of the spectrum
resultant the sum of two or more vectors.
retroreflector see corner-cube prism
उत्क्रमणीय अभिक्रिया reversible reaction A reaction in which the products can make reagents, as well as the reagents making products.
reversion right-to-left reversion of an image
Reynold’s number characterizes the onset of turbulence in a tube. Re = 2vr(rho)/n, where n=viscosity, r=radius of tube, rho=density of the fluid, v=velocity of the fluid; If Re<2000, there is laminar flow; if Re>2000, there is turbulent flow.
RHME rotating hanging meniscus electrode
rhomboid prism used for lateral deviation of a light ray
rolling friction the friction from when one body rolls across a surface; generally much smaller than the sliding friction.
वर्ग मूल माध्य वेग root mean square velocity (RMS velocity) The square root of the average of the squares of the individual velocities of the gas particles in a mixture. To put it in a way that a normal human can understand, it's the average of how fast the particles in a gas are going (assuming you ignore the direction they're traveling in).
root-mean-square speed (rms) the square root of the average of the squared speeds of gas molecules in a sample.
Roots blower a type of vacuum pump capable of pressures down to .01 torr.
rotating disk electrode (RDE) method to determine kinetics of electrodes. If you have the electrode be a rotating disk, the current of the sample can be related to the speed of rotation.
Rowland ghosts spurious intensity maximum spurred from periodic errors in the spacing of the ruled grooves in a diffraction grating.
RPM radical pair mechanism
ruby aluminum oxide, Al2O3
लवण salt An ionic compound.
SAM self-assembled monolayer
sapphire Al2O3, aluminum oxide
SATP standard ambient temperature and pressure; corresponds to 25 C, 1 bar
संतृप्त saturated When the maximum amount of solute is dissolved in a liquid
scalar a quantity that is specified completely by giving a number
SCE standard calomel electrode
Schott IRG 11 calcium aluminate; transmits light between .3-5.5 microns
Schott IRG 2 germanate; transmits light between .3-4.6 microns
Schott IRG N6 calcium aluminosilicate; transmits light between .3-4.75 microns
SCRF self-consistent reaction field method. A method for calculating the energies of molecules in a reaction
उष्मागतिकी का द्वितीय नियम Second law of thermodynamics Whenever you do something, the universe gets more random.
second law of thermodynamics the entropy of an isolated system increases in the course of a spontaneous change
Seeback effect when a metal has a temperature gradient, it has a voltage. The difference in thermally induced voltages of two metals will cause a net voltage in a junction.
अर्धचालक semiconductor A substance that conducts electricity poorly at room temperature, but has increasing conductivity at higher temperatures. Metalloids are usually good semiconductors.
SERR spectroscopy surface-enhanced resonance Raman spectroscopy; a Raman method used because it has excellent selectivity to the microscopic environment and orientation of things adsorbed on surfaces.
SERS surface-enhanced Raman scattering
SHE standard hydrogen electrode; defined as having 0V.
shear modulus the modulus of rigidity; concerned with the elastic deformation of a body in which an applied force results in the shape of a body.
SHG second harmonic generation
shielded when the sigma value in NMR is greater than zero. Deshielding is when the value is less than zero.
shielding effect The outer electrons aren't pulled very tightly by the nucleus because the inner electrons repel them. This repulsion is called the shielding effect, and can be used to explain lots of neat-o stuff.
सिग्मा बन्ध sigma bond A real fancy way of saying "single bond"
significant figure The number of digits in a number that tell you useful information. For example, when you weigh yourself on a bathroom scale, it says something like 150 pounds rather than 150.32843737 pounds. Why? Because the thing can only weigh accurately to the nearest pound. Any other digits that are on this number don't mean anything, because they're probably wrong anyway.
silicon controlled rectifier a switching device; in the on state it has low resistance and in the off state it has very high resistance.
single-displacement reaction (a.k.a. single replacement reaction) When one unbonded element replaces an element in a chemical compound. These are frequently redox reactions.
size exclusion chromatography (SEC) where you separate mixtures based on the sizes of the molecules.
SLAR single layer antireflection coating
smectic a smectic phase is when the molecules align themselves into a pseudo-crystalline lattice. Liquid crystals are one example.
Snell’s law n1sin(theta1)=n2sin(theta2); describes refraction.
softening point the point at which a glass can be molded or worked
sol a stable dispersion of either solids in liquids or solids in solids.
solenoid a long coil of wire consisting of may loops; when current flows through it, the magnetic field resembles that of a bar magnet.
बिलेयता solubility A measurement of how much of a solute can dissolve in a liquid.
बिलेयता गुणनफल स्थिरांक solubility product constant Abbreviated Ksp, this value indicates the degree to which a compound dissociates in water. The higher the solubility product constant, the more soluble the compound.
विलेय solute The solid that gets dissolved in a solution.
विलायक solvent The liquid that dissolves the solid in a solution.
space-charge effect used to describe particle beam aberrations, it arises from the natural repulsion of particles of like charge; a focused beam will disperse, giving a diffuse image.
spatial coherence how much the waves are in step as they leave a laser cavity.
special theory of relativity 1) The basic laws of physics are the same in all inertial reference frames. 2) Light propagates through empty space with a definite speed c independant of the speed of the source or observer.
specific gravity the ratio of the density of a substance at 4 C to that of water at 4 C.
विशिष्ट उष्मा धारिता specific heat capacity The amount of heat required to increase the temperature of one gram of a substance by one degree.
spectator ions The ions in a reaction that don't react.
speed of sound equal to the square root of the bulk modulus/density of the medium. As temperature rises, so does the speed of sound.
sphere radius=4pi(r squared), volume=4/3pi(r cubed)
spherical aberration the variation of focus with aperture in which a ray through the edge of the lens intersects the axis at a point other than the paraxial focus.
spinel magnesium aluminate, MgAl2O4.
spin-spin coupling constant (J) defines how much of an interaction you have between nuclei in a molecule. Gives rise to the fine structure in NMR.
spontaneous change A change that occurs by itself. All exothermic reactions are spontaneous. However, this doesn't mean that all exothermic reactions are fast. The combustion of gasoline is spontaneous, but not very fast unless you add a little energy.
SPT sputtering; allow a material into the vapor phase to condense into a thin film
sputtering see SPT
standard state the pure form of a substance at 1 bar pressure for any given temperature.
मानक ताप व दाब standard temperature and pressure One atmosphere and 273 K.
steric hindrance This is the idea that the functional groups on big molecules get in the way of a chemical reaction, making it go slower. Imagine a fat guy trying to get into a Honda Prelude - that's steric hindrance.
stoichiometry The art of figuring how much stuff you'll make in a chemical reaction from the amount of each reagent you start with.
stopband the primary region of reflection or absorption of a rejection filter.
STP See standard temperature and pressure.
STP standard temperature and pressure; corresponds to 0C, 1 atm.
streamline the path taken by any particle in a steady, laminar flow.
strong acid An acid that fully dissociates in water
strong nuclear force The force that holds the nucleus together. As the name suggests, this force is strong.
structural formula See Lewis structure.
उर्ध्वपातन sublimation When a solid can change directly into a gas. Dry ice does this.
superconductor A material which has no resistance to electricity. When passing current through a superconductor, there is no loss of electrical power due to these materials.
अतिशीतलन supercooling When you cool something below its normal freezing point
supercritical liquid a liquid which exists at temperatures above the normal boiling point; this is brought about through high pressure. Reactivity of solutes in these liquids can be changed drastically with minor changes in temperature and pressure.
superfluid a fluid that flows without viscosity (ex: He-II)
superhigh surface area carbon any carbon which has a specific surface area greater than 2630 square meters per gram
superionic materials Materials which exist largely in the ion phase. These are extremely useful in making conductors which work via ionic migration.
अतिसंतृप्त supersaturated When more solute is dissolved in a liquid than is theoretically possible. This doesn't happen much, as you might imagine.
supersaturated vapor A vapor which will spontaneously begin to condense in the presence of nucleation centers.
पृष्ट तनाव surface tension A measurement of how much the molecules on a liquid tend to like to stick to each other. If something has a high surface tension, it likes to bead up.
surface tension (gamma); the force F per unit length L that acts across any line in a surface, tending to pull the surface closed.
surfactant a species that is active between two phases. It accumulates at the interface and changes the surface tension.
suspension A mixture that looks homogeneous when you stir it, but where the solids settle out when you stop. Mud is a very short-lived suspension, while peanut butter is a very long-lived suspension.
syngas a mixture of gases (largely carbon monoxide and hydrogen) that results from heating coal in the presence of steam. Can be used as a fuel.
synthesis When you make a big molecule from two or more smaller ones.
system Everything you're talking about at the moment.
TDFS time-dependent fluorescence shifts
TEM transmission electron microscopy. What you do is take the sample, grind it up, then place an aqueous suspension of it on a grid where the electron microscope can get at it.
ताप temperature A measurement of the average kinetic energy of the particles in a system.
temporal coherence how much waves stay in step along a beam path
theoretical plates represents how many times you do a separation in purification; can be used to describe column chromatography, GC, or HPLC.
theoretical yield The amount of product which should be made in a chemical reaction if everything goes perfectly.
thermal motion chaotic, random motion of molecules due to the temperature
thermal neutrons neutrons that have not been slowed down and have reached equilibrium with matter at room temperature
thermionic emission you can get a current to flow from a heated filament to a positive electrode in a vacuum; this emission is simply electrons flowing from the filament to the positive electrode.
thermistor a substance which changes its resistance with temperature. Those developed as infrared detectors are known as bolometers.
thermocouple two metals are put together side by side when heated, one metal expands more than another due to differences in the coefficients of thermal exansion, and the strip bends. This can be used as a switch, as in a thermostat.
उष्मागतिकी thermodynamics The study of energy
thermogravimetric analysis (TGA) when you heat a sample to observe weight changes; used when studying the loss of waters of hydration or CO2.
thermoplastics plastics that can be softened by heating and return to their original state on cooling.
thermopneumatic detector when the radiation incident on a gas in a closed chamber increases the temperature and pressure of a gas, a mirror on the cell wall moves. This movement is measured optically, and can be used to determine the amount of radiation incident on the cell.
thermovoltaic detector an IR detector where temperature changes of a junction of dissimilar metals because of changes in the level of incident radiation causes a change in voltage.
उष्मागतिकी का तृतीय नियम Third law of thermodynamics The randomness of a system at 0 K is zero.
time dilation the idea that time travels slower for somebody in a moving reference frame; consequence of relativity.
time-of-flight (TOF) when you apply the same translational energy to all particles; the lighter particles will travel a shorter distance over a charged plate because there is less momentum to carry them forward.
titration When the concentration of an acid or base is determined by neutralizing it.
total binding energy energy required to break a nucleus into its component protons and neutrons
total internal reflection second harmonic generation (TIR SHG) This is what happens when you shine the exitation beam and probe beam on a liquid-liquid surface. What you are counting on happening is that the beams will reflect off of the bottom liquid and give the second harmonic signal you’re looking for.
transducer a device that turns one kind of energy to another (like a loudspeaker turns electrical energy to sound); a device that converts a light signal into an electrical signal
transient grating techniques what you do in one of these studies is to get several beams coming into a sample that have different circular polarity. Their interference sets up a diffraction grating which can be used to run experiments.
transistor a device used to give current and power amplification
transition state See "activated complex"
transverse relaxation time (T2) the time it takes after a pulse in NMR for the spins to get out of phase with one another. This is also called the spin-spin relaxation time.
transverse wave when a wave has the property that the particles of the wave move perpindicular to the motion of the wave itself, such as a water wave.
TREPR time-resolved electron paramagnetic resonance; a way of identifying transient radicals
trichroism exhibits different colors in 3 different directions when viewed by transmitted light
triple point The temperature and pressure at which all three states of a substance can exist in equilibrium.
tungsten filament an IR light source where the emitter is a tungsten filament; the IR output range is limited by the window material, although the window material may actually heat up enough to serve as a blackbody emitter.
tunneling the penetration of a particle into a classically-forbidden region.
turbulent flow when a moving liquid exhibits erratic, whirlpool-like currents.
Turing pattern patterns that arise from oscillatory coupled cells. AI.
two-dimensional NMR A method in which you can take NMR peaks that are stuck on top of each other and separate them. The plot has one axis as the normal NMR axis, and the other corresponds to the spectrum when you hit the sample with 90 degree radiation.
Tyndall effect the scattering of visible light by a colloidal dispersion.
UHV ultrahigh vacuum
ultrasonic sound waves that have frequency higher than we can hear (20,000 Hz)
uniphase a wavefront is uniphase if it has the same phase at all points
unipotential lens see einzel lens
unit cell The simplest part of a crystal that can be repeated over and over to make the whole thing.
असंतृप्त unsaturated When you haven't yet dissolved all of the solute that's possible to dissolve in a liquid.
unshared electron pair two electrons that aren't involved in chemical bonding. Also frequently referred to as a "lone pair".
Vacuum ultraviolet (VUV) UV radiation of high enough frequency that air will absorb it. UHV is ultrahigh vacuum-UV, which is of higher frequency still.
valence electron The outermost electrons in an atom.
Van der Waals picture of condensed matter molecular dynamics of dense fluids are determined primarily by the size and shape of molecules; that is, the short-range repulsive internuclear forces.
वाष्प दाब vapor pressure The pressure of a substance that's present above it's liquid. For example, you can tell that ammonia has a high vapor pressure because the smell of it is very strong above liquid ammonia.
वाष्पन vaporization When you boil a liquid.
vector a quantity that has both direction and magnitude, such as velocity.
velocity selector used with molecular beams; slotted disks that make sure only particles with the desired speed reach the target.
Venturi tube a pipe with a narrow constriction; if it has an opening at this constriction, it will tend to pull a vacuum through it equal to the vapor pressure of the liquid; a consequence of Bernoulli’s principle
viscosity the internal friction of a liquid
visible spectrum radiation of wavelength 400-750 nm.
volatile A substance with a high vapor pressure.
voltage equal to the potential difference between two things.
VOM volt-ohm-meter; a multimeter that measures voltage, current and resistance
VSEPR A theory for predicting molecular shapes that assumes that electrons like to be as far from each other as possible.
Walden reductor a metal reduction column filled with silver
Walsh diagram a diagram that shows the variation of orbital energy with molecular geometry
Wedge prism used for beam steering
Welsbach mantle a gauze mesh, similar to the one in gas lanterns, impregnated with ThO2 and a small amount of CeO2 which is heated by either a burning gas or electric charge. It gives off IR radiation between 10-100 microns.
X-ray fluorescence spectroscopy (XRF) measures the energies of the inner electrons of an atom by knocking them off with X-rays; good for about 35 elements. Handy because it is not a destructive method of analysis - the electrons are simply elevated to outer orbitals and the relaxation to the inner orbitals is measured.
Young’s modulus (E) the ratio of longitudinal stress to longitudinal strain.
Zeeman effect this is the effect of overcoming the normal degeneracy of electron spin states by applying a magnetic field which can interact with the magnetic moment of the electron. This is observed when atoms are subjected to a powerful magnetic field resulting in the spectral lines being split into a number of component lines.
zeroth law of thermodyamics If A is in thermal equilibrium with B and B is in thermal equilibrium with C, then A and C are in thermal equilibrium
ZSM-5 zeolites Commonly used zeolites which are extremely good at removing NOx. Used in auto emissions control and direct composition of NO to N2 and O2.

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