Abstract

We have theoretically studied the nonadiabatic transitions among the lower states with W = 1_u symmetry {1_u (Lindeman and Wiesenfeld, 1979) to 1_u (Alexander et al., 2000)} in the photodissociation of Br₂ using the complete active space self-consistent field (CASSCF) computations and the time-independent Schrodinger equations. The CASSCF wave function is formed from a complete distribution of a number of active electrons in a set of active orbitals, which in general constitute a subset of the total occupied space. From the configuration analysis of the CASSCF wave functions, we found that the nonadiabatic transition between 1_u(Bracker et al., 1999) and 1_u (Lindeman and Wiesenfeld, 1979) is a noncrossing type, while that between 1_u (Bracker et al., 1999) and B³P_0+u is a crossing type. The spectroscopic constants for the X¹S_g⁺, A³P_1u and B³P_0+u states of Br₂ have been calculated. The absorption cross-section for the ground and the lower excited states in the photodissociation of Br₂ molecule has been presented as well as the numerical estimates of nonadiabatic transition probabilities. Also, the five highest occupied and the five lowest unoccupied orbitals of Br₂ have been calculated.

Key words: Nonadiabatic transitions, broimine molecule, photodissociation.