Page 182 - Academic Press Encyclopedia of Physical Science and Technology 3rd Analytical Chemistry

P1: GRB/MBQ P2: GLM Final Pages Qu: 00, 00, 00, 00
Encyclopedia of Physical Science and Technology EN007C-340 July 10, 2001 14:45

Infrared Spectroscopy

Norman B. Colthup
American Cyanamid Company

I. Basic Theory
II. Instrumentation
III. Sample Handling Techniques
IV. The Near Infrared Region
V. Quantitative Analysis
VI. Group Frequencies

GLOSSARY beams and then recombines them, resulting in inter-
ferences that depends on the path length difference be-
Absorbance Vertical coordinate used for infrared spectra tween the two beams.
that is equal to the log of the reciprocal of the sample Monochromator Device that separates radiation having
transmittance. a single frequency from radiation having many differ-
Absorptivity Constant characterizing the capacity of a ent frequencies.
sample to absorb radiation of a specific wavelength, Normal coordinate Single coordinate defined in such a
independent of sample thickness or concentration. way that it describes the effective amplitude of a normal
Dipole moment Magnitude of the positive or negative mode of vibration in a molecule.
charge constituting a dipole, multiplied by the spacing Normal mode Vibration where each Cartesian coordi-
between the charges. nate of every atom in the molecule oscillates with the
Fermi resonance Quantum mechanical interaction be- same frequency and goes through the equilibrium point
tween close-lying energy states of a fundamental and at the same time; there is no molecular translation or
an overtone or combination that shifts the absorption rotation.
frequencies and redistributes the intensities. Oscillator Mass or group of masses that vibrate at certain
Fundamental Band in the infrared spectrum that results frequencies.
from a change from the vibrational ground state to the Overtone Band in the infrared spectrum that results from
first excited vibrational state of a molecule. a change from the vibrational ground state to the second
Group frequency Frequency region of the spectrum or a higher vibrational state of a molecule.
where absorption is expected when a chemical func- Photon Individual particle or quantum of radiation.
tional group such as a carbonyl is present in a molecule. Transition Change from one quantum mechanically de-
Interferometer Device that splits radiation into two fined energy state to another.

793