Theoretical study of nonadiabatic transitions in the photodissociation of Cl2 and Br2

Lower-lying potential curves of Br-2 are calculated by the spin-orbit configuration interaction method, and the spin-orbit branching mechanisms in the photodissociation processes are examined. The second absorption band at 227 nm is assigned unambiguously to the transition from the X(1)Sigma(g)(+) to the (3)Sigma(1u)(+) (sigma(g) --> sigma(u)(*)) state. The calculated potential curves and the radial derivative coupling elements of Cl-2 and Br-2 are used to evaluate the nonadiabatic transition probabilities by solving the time-dependent coupled Schrodinger equations semiclassically. The different nonadiabatic behavior in Cl-2 and Br-2 is analyzed in terms of the differences in the electronic factors and the reduced mass. (C) 2003 Elsevier Science B.V. All rights reserved.