Page 282 - Academic Press Encyclopedia of Physical Science and Technology 3rd Analytical Chemistry

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Encyclopedia of Physical Science and Technology EN009N-447 July 19, 2001 23:3

Microwave Molecular

Spectroscopy

Robert L. Cook
Mississippi State University

I. Background
II. Experimental Techniques
III. Evaluation of the Moments of Inertia
IV. Rigid-Rotor Energy Levels and Spectra
V. Centrifugal Distortion Effects
VI. Rotation–Vibration Interactions
VII. Internal Rotation
VIII. Evaluation of Molecular Structures
IX. Stark Effect and Zeeman Effect
X. Nuclear Quadrupole Hyperfine Structure
XI. Advanced Experimental Methods

GLOSSARY sample cell. Can be used to simplify complicated
spectra.
Asymmetric top Molecule for which all three principal Effective constants Values of molecular parameters av-
moments of inertia are different. eraged over the vibrational motion, and hence associ-
Asymmetry parameter Measure of the departure of a ated with a given vibrational state. For example, the
molecule from the rotational behavior of a symmetric- effective rotation and distortion constants.
top molecule. Equilibrium constants Values of molecular parameters
Centrifugal distortion Molecular rotation gives rise to associated with the minimum in the vibrational poten-
a centrifugal force causing the bond lengths and bond tial function, the so-called vibrationless state. For ex-
angles to change slightly. This leads to shifts of the ample, the equilibrium bond distance.
rotational lines. Hyperfine structure Splitting of spectral lines into two
Double resonance Technique in which two radiation or more components. This can arise, for example,
fields (a pump and a probe) are introduced into the from the application of external fields (electric and

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