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Vibronic intensity distributions in the electronic spectra of polyatomic molecules

1966; IOP Publishing; Volume: 89; Issue: 4 Linguagem: Inglês

10.1088/0370-1328/89/4/326

1747-3810

W. L. Smith,

Advanced Chemical Physics Studies

Intensity distributions in progressions in non-totally symmetric vibrations are discussed. It is shown that these distributions can be expressed in concise form as the terms in certain simple series of the form (1 - x)-n/2, where n is a positive integer, x = {(ν" - ν')/(ν" + ν')}2 and ν', ν" are the vibration frequencies in upper and lower states respectively. For the progressions vl <- ll v = l, l+2, l+4,... in electronically allowed systems, the intensity of the band vl <- ll relative to that of the band ll <- ll is given by the {½(v - l + 2)}th term in the series (1 - x)-(2[vertical line]l[vertical line]+d)/2, where d is the degeneracy of the vibration, v is the vibrational quantum number and [vertical line]l[vertical line] = 0 (d = 1) or v, v - 2,..., 0 or 1 (d = 2, 3). It is also shown that (intensity of band ll <- ll)/(Σν intensity of band vl <- ll) = q2[vertical line]l[vertical line]+d where q = (ν'ν")½/½(ν' + ν").