A REFINED POTENTIAL-ENERGY FUNCTION FOR THE ELECTRONIC GROUND-STATE OF NO2

The potential energy surface for the electronic ground state of the NO 2 molecule is optimized by means of a variational procedure using the exact vibrational Hamiltonian in the bond length-bond angle coordinate s. 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. Jest (1991, J. chem. Phys., 95, 5686) are involved. The standard devia tion 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) obtaine d using an exact Hamiltonian. The refined potential is a reasonable ap proximation to the true potential at energies below the conical inters ection.