Rotation-Vibration Interactions In (Hf)(2). Ii. Rotation-Vibration Interactions In Low-Lying Vibrational States

Results of a six-dimensional treatment of the rotation-vibration Hamiltonian for (HF)(2) are presented. Energies of 40(J + 1) states for J less than or equal to 4 are reported. These energies and the corresponding wave functions are used to analyze rotation-vibration interactions in (HF)(2). Over the range of energies probed in this study, Coriolis couplings are found to be relatively unimportant and for 94% of the states the wave functions and energies can be approximated by the solutions to a Hamiltonian in which the Coriolis coupling terms are neglected. Rotation-vibration interactions are investigated in greater detail for the ground state and for states with one and two quanta of excitation in the intermolecular stretching vibration upsilon(4). Specifically, we study the K and n(4) dependencies of the tunneling splitting and the effective rotational constant that corresponds to rotation about the intermolecular axis. Based on an analysis of the wave functions and the potential, we find that the observed trends can be attributed to the fact that (HF)(2) behaves like a quasilinear molecule whose large amplitude bending motions lead to significant wave amplitude in linear configurations, even in the vibrational ground state. (C) 1999 American Institute of Physics. [S0021-9606(99)02505- 2].