A refined potential energy function for the electronic ground state of NO₂

Abstract

The potential energy surface for the electronic ground state of the NO₂ molecule is optimized by means of a variational procedure using the exact vibrational Hamiltonian in the bond length-bond angle coordinates. In the optimization, the potential energy function of S. A. Tashkun and P. Jensen (1994, J. molec. Spectrosc., 165, 173) is taken as the starting point and the observed band origins given by A. Delon and R. Jost (1991, J. chem. Phys., 95, 5686) are involved. The standard deviation of this fitting for the 142 vibrational levels below 9000 cm⁻¹ is 2·08 cm⁻¹, and that of Tashkun and Jensen is 14·28 cm⁻¹ obtained using an exact Hamiltonian. The refined potential is a reasonable approximation to the true potential at energies below the conical intersection.