TF02		15min1:47

G. DUXBURY, B. D. MCDONALD, Department of Physics and Applied Physics, Strathclyde University, Glasgow G4 0NG, Scotland, U.K.; CH. JUNGEN, Laboratoire Aimée Coton de CNRS, Université de Paris-Sud, 91405 Orsay CEDEX, FRANCE; A. ALIJAH, Facultät für Chemie, Universität Bielefeld, D-4800 Bielefeld, Germany.

Fermi resonance effects on Renner-Teller coupling in NH₂ and CH₂ have been identified. We have developed an extension of the semi-rigid bender approach of Jungen and Merer and of Duxbury and Dixon to calculate the interplay between Renner-Teller and vibrational resonances in detail. The basic idea is that if in the semi-rigid bender the bond length relaxes to follow the minimum on the potential energy surface, the effect of the stretch-bend coupling should be minimised in this basis. This should simplify the calculations compared to those using a full three dimensional basis when only a few quanta of the stretching vibrations are excited via resonances. The effects of the interplay between Renner-Teller and vibrational coupling will be discussed using some of the most recent data obtained for the b state of CH₂, making use of two-dimensional wavefunctions without and with Fermi resonance effects.