Calculations of rotation-vibration states with the z axis perpendicular to the plane: High accuracy results for H_3~+

摘要

A method of calculation of rotation-vibration states for a general triatomic that places the body-fixed z axis perpendicular to the plane of the molecule is implemented within a discrete variable representation (DVR) for the vibrational motion. Calculations are presented for water and H_3~+. For H_3~+ the new method improves on previous high accuracy ab initio treatments of the rotation-vibration energies of the molecule both in accuracy and the range of rottional states that can be treated. Reliable treatment of quasilinear geometries means that tahe method is also promising for treating very highly excited states.