Spin-orbit branching in the photofragmentation of HCl at long wavelength

We report a new experimental determination of the branching ratio for formation of ground state Cl(P-2(3/2)) and spin-orbit excited Cl(P-2(1/2)) fragments subsequent to excitation of the HCl molecule to the repulsive A (1) Pi electronic state. Our work extends previous experimental measurements well into the long-wavelength tail of the A (1) Pi <-- X-1 Sigma(+) absorption profile. The branching into the spin-orbit excited Cl(P-2(1/2)) fragment is found to reach a maximum near 220 nm, before falling to zero at threshold. Our new measured branching fractions are reproduced nearly quantitatively by new calculations which supplement those reported previously [M. H. Alexander, B. Pouilly, and T. Duhoo, J. Chem. Phys. 99, 1752 (1993)]. (C) 1998 American Institute of Physics.