INTERNAL COORDINATE FORMULATION FOR VIBRATION-ROTATION ENERGIES OF POLYATOMIC-MOLECULES V - ZEROTH-ORDER SEPARATION FOR NONPRINCIPAL AXIS SYSTEMS

The theory of vibration-rotation interactions in polyatomic molecules using curvilinear internal coordinates for the vibrational degrees of freedom is extended to the situation where the initial molecular axis system is not the principal axis system of the equilibrium configurati on. For this new situation, the transformation coefficient rho(1)(1) i s derived as well as the vibrational coefficients (G(tt')(-1))(0). Thi s new transformation may not be useful nor necessary when all of the i nternal motions are of small amplitude. However, in the case of vibrat ion-rotation-internal rotation interactions, the new transformation is helpful when the internal rotor is a symmetric top and necessary when the internal rotor is an asymmetric top. (C) 1998 Academic Press.