Nonadiabatic wave packet dynamics on the coupled X²A<inf>1</inf>/ A²B<inf>2</inf> electronic states of NO<inf>2</inf> based on new ab initio potential energy surfaces

Abstract

We report new accurate ab initio potential energy surfaces (PESs) for the ground (X2A1) and first excited (A2B2) electronic states of NO2. The adiabatic potential energy data are calculated by the configuration-selecting multi-reference configuration-interaction method employing the cc-pVTZ basis set. We diabatize the adiabatic potential energy data and investigate the nuclear dynamics on these coupled electronic states by a time-dependent wave packet method. First, we investigate the photodetachment spectrum of NO2/- for a transition to the A2B2 state and compare our findings with the available experimental results. The agreement is very satisfactory. In addition, we examine the femtosecond decay of the A2B2 diabatic electronic population revealing the impact of the nonadiabatic coupling on the time-dependent dynamics (internal conversion process) of NO2. The present study based on more accurate ab initio PESs enables us to confirm our earlier estimate of the vibronic coupling strength near the energetic minimum of the X2A1-A2B2 crossing seam. (C) 2000 Elsevier Science B.V.