Vibrational perturbation in the ground and first vibrationally excited states of trans methyl nitrite

Abstract

In an N-atomic molecule with a nearly free internal rotation the interaction of the 3N-7 vibrational modes with the rotation-internal rotation motion produces a modification of the rotation and internal rotation constants in the Hamiltonian. The modifications of these constants were explicitly deduced by us (1) in terms of the Coriolis coupling between vibration and overall rotation and internal rotation and torsional angle derivatives of the normal coordinates. In this work we have numerically evaluated the modification of the rotation-internal rotation constants in the ground and first vibrationally excited states (v 14 =1) of trans methyl nitrite which has a very low barrier (V 3 =10 cm −1 ) methyl rotor (2)