A potential energy surface for the electronic ground state of CO2

Abstract

The potential energy surface for the electronic ground state of CO2 is refined by means of a two-step variational procedure using the exact rovibrational Hamiltonian in the bond length–bond angle coordinates. In the refinement, the observed rovibrational energy levels for J=0–4 below 16,000 cm−1, obtained from the effective spectroscopic constants of CO2 given by Rothman et al. (J Quant Spectrosc Radiat Transfer 1992, 48, 537) in the HITRAN data base, are used as the input data points. The accurate ab initio force constants of Martin et al. (Chem Phys Lett 1993, 205, 535) are taken as the initial guess for the potential. The root-mean-square error of this fit to the 431 observed rovibrational energy levels is 0.05 cm−1. With the optimized potential energy surface, we also calculate the rovibrational energy levels of 13C16O2 and 12C18O2. The results are in good agreement with experimental data. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 269–280, 2000