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

Abstract

We report a new experimental determination of the branching ratio for formation of ground state Cl(2P3/2) and spin–orbit excited Cl(2P1/2) fragments subsequent to excitation of the HCl molecule to the repulsive A 1Π electronic state. Our work extends previous experimental measurements well into the long-wavelength tail of the A 1Π←X 1Σ+ absorption profile. The branching into the spin–orbit excited Cl(2P1/2) 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)].