Infra-Red Spectra of Axially Symmetric XY3Z Molecules I. Vibration-Rotation Energies

The vibration-rotation energies of the axially symmetric XY3Z molecular model are investigated to second order of approximation, including cubic and quartic anharmonic terms in the potential energy, all Coriolis interactions between rotation and vibration, centrifugal stretching and dependence of the rotational constants on the vibrational state. The energies are expressed in term value form, E=hc(GV+FR—FC), where GV, FR and FC are, respectively, the vibrational, rotational, and Coriolis terms which are given explicitly as functions of the molecular constants appearing in the Hamiltonian.