Nonadiabatic wave packet dynamics on the coupled (X)over-tilde(2)A(1)/(A)over-tilde(2)B(2) electronic states of NO2 based on new ab initio potential energy surfaces

We report new accurate ab initio potential energy surfaces (PESs) for the g round ((X) over tilde (2)A(1)) and first excited ((A) over tilde B-2(2)) el ectronic states of NO2. The adiabatic potential energy data are calculated by the configuration-selecting multi-reference configuration-interaction me thod employing the cc-pVTZ basis set. We diabatize the adiabatic potential energy data and investigate the nuclear dynamics on these coupled electroni c 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 femtosecon d decay of the (A) over tilde B-2(2) diabatic electronic population reveali ng the impact of the nonadiabatic coupling on the time-dependent dynamics ( internal conversion process) of NO2. The present study based on more accura te ab initio PESs enables us to confirm our earlier estimate of the vibroni c 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 r ights reserved.