The vibration–rotation kinetic energy operator for sequentially bonded tetra-atomic molecules in internal coordinates

Abstract

An exact vibration–rotation kinetic energy operator for polyatomic molecules has been obtained. Using this Hamiltonian for sequentially bonded tetra-atomic molecules, all rovibrational terms have been derived with internal coordinates as the vibrational variables. The present approach is greatly simplified with less algebra compared with conventional methods. Also, simple and explicit expressions for the vibration–rotation coupling terms in internal coordinates are presented.