Rovibrational interactions in linear triatomic molecules: a theoretical study in curvilinear vibrational coordinates

Abstract

A variational solution to the rovibrational problem in curvilinear vibrational coordinates has been implemented and used to investigate the nuclear motions in several linear triatomic molecules, like HCN, OCS, and HCP. The dependence of the rovibrational energy levels on the rotational quantum numbers and the l-doubling has been studied. Two approximations to the rovibrational Hamiltonian have been examined, depending on the level of truncation of the potential energy operator. It turns out that truncation after the fifth order in the potential is sufficient to produce vibrational energies of high accuracy. An interesting feature of the present formulation of the problem in terms of the curvilinear vibrational coordinates is the explanation for the l-doubling of the rovibrational levels, which in this picture is interpreted as the result of the inequivalency of the average rotational constants in mutually perpendicular planes, rather than as the effect of the Coriolis-type interactions between the vibrational and rotational motions. The present theoretical results are compared with the available experimental data from high-resolution spectroscopy, as well as with other ab initio calculations.

A highly accurate potential energy surface for carbonyl sulphide (OCS): how important are the ab initio calculations?

“…The purpose of this paper is twofold: (i) to critically evaluate the influence of the underlying ab initio calculations in the context of empirical refinement of the PES, and (ii) to produce the most accurate PES of the electronic ground state of OCS in the literature. There have been several theoretical studies of the PES and rovibrational spectrum of OCS 12–19 but none at the accuracy or completeness targeted in this study.…”