Nonadiabatic wave packet dynamics on the coupled (X)over-tilde2A1/(A)over-tilde2B2 electronic states of NO2 based on new ab initio potential energy surfaces

We report new accurate ab initio potential energy surfaces (PESs) for the ground ((X) over tilde (2)A(1)) and first excited ((A) over tilde B-2(2)) 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 (A) over tilde B-2(2) State and compare our findings with the available experimental results. The agreement is very satisfactory. In addition, we examine the femtosecond decay of the (A) over tilde B-2(2) 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 (X) over tilde (2)A(1)-(A) over tilde B-2(2) crossing seam. (C) 2000 Elsevier Science B.V. All rights reserved.