Spin-orbit branching in the photodissociation of HF and DF. I. A time-dependent wave packet study for excitation from v=0

The photodissociation dynamics of HF and DF, following A (1)Pi <-- X (1)Sig ma(+) electronic excitation, are examined using time-dependent wave packet techniques. The calculations are based on new multireference configuration interaction calculations of the potential energy curves and complete active space self-consistent field calculations of the off-diagonal spin-orbit co upling matrix elements. The calculated branching fraction for the formation of excited state fluorine, F*(P-2(1/2)), following excitation from the gro und vibrational state (v=0) of HF, agrees well with the value of 0.41 +/- 0 .08 measured experimentally at 121.6 nm by Zhang [J. Chem. Phys. 104, 7027 (1996)]. Predictions are made for the excited spin-orbit state branching fr action for both HF and DF over a wide range of photon excitation energies. The results for HF and DF are discussed in context with the corresponding r esults for the photodissociation of HCl and DCl. (C) 2000 American Institut e of Physics. [S0021-9606(00)01529-4].