VIBRATIONAL TRANSITIONS OF COUPLED STRETCHING AND BENDING OVERTONES IN CHLOROFORM

The intensities and frequencies of Fermi-coupled stretching and bendin g overtone transitions in CHCl3 were calculated by means of a variatio nal method. Symmetrized two-dimensional ab initio potential and dipole moment surfaces were determined at the MP2 level using the 6-31G* ba sis set. The Hamiltonian for the CH- stretching motion and the simulta neously excited twofold degenerate CH- bending vibration is expressed most easily in cylindrical coordinates. Absorption intensities up to t he Delta v = 7 CH-stretching overtone above 16 300 cm(-1) are calculat ed and are compared to former experimental values and theoretical resu lts. New quantitative intracavity measurements for the N = 6 polyad ar e presented. Relative errors between absolute experimental intensities and the calculated values are less than 30%. (C) 1995 American Instit ute of Physics.