Rotational distortion INDEX

Here vq is the rotationless transition frequency corresponding to AG, the spacing between the two vibrational levels with J= 0. B and B" are the rotational constants of the upper and lower states, respectively, and the index m = - Jfor Pbranch lines, J + 1 for Pbranch lines. The centrifugal distortion constants are extremely small (typically 10 cm ), and it is assumed that Dl = IX = D ... 

In crystalline solids the effects of randomness of environment and of quantized rotation are absent, and very sharp vibration bands can be observed (Rgure 8.7(c)), especially in the Raman Effect. Surface reflection effects vary a lot in the vicinity of an IR absorption band (because the refractive index of the sample varies - a phenomenon known as anomalous dispersion) and distort its apparent profile (known as the Christiansen effect). Samples must be prepared very carefidly by fine grinding, to ensme that high quality spectra can be obtained. 

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