INTENSITIES OF HOT-BAND TRANSITIONS - HCN HOT BANDS

A simple vibrational Honl-London-type formula for hot-band intensities is tested by measuring the intensities of a number of vibrational tra nsitions, including many hot bands, for HCN. This vibrational intensit y formula is based on one- and two-dimensional harmonic oscillator fun ctions and a nonlinear electric dipole function that is expanded in a Taylor series with respect to the normal coordinates. It is shown that , when this formula is included, the observed transition dipoles for t he bending hot bands differ by only a few percent from the transition dipoles for the same quantum number changes from the ground state. Inf rared absorption intensity measurements are given for the transition d ipoles for the transitions 01(1)0-00(0)0, 02(0)0-00(0)0, 03(1)0-00(0)0 , 04(0)0-00(0)0, 10(0)0-01(1)0, 12(0)0-00(0)0, and 20(0)0-00(0)0 and t he accompanying hot bands involving the lower states v(2) = 1, 2, and 3. This simple model is limited to well-behaved systems, but would be useful for estimating the intensities of some high-temperature spectra . For HCN the Herman-Wallis constants that are quadratic in J(or m) ar e shown to be determined principally by the effect of l-type resonance . (C) 1995 Academic Press, Inc.