Spin–orbit branching in the predissociation of the C 1Π state of HCl and DCl: a manifestation of quantum interference Original Research Article

We report a combined theoretical–experimental investigation of the predissociation of HCl subsequent to photoexcitation of the lowest Rydberg state of 1Π symmetry (C 1Π). Our particular interest is the characterization of the configurational mixing between this state and the lower, repulsive valence state of 1Π symmetry (A 1Π). A plausible model for the coupling between these two states, which also involves spin–orbit coupling between the C-state and the a 3Π1 and t 3Σ1+ states, leads to predicted spin–orbit branching ratios, for both HCl and DCl, which agree qualitatively with the results of a new experimental investigation, also reported here. The theoretical simulation further strongly suggests that the observed predissociation branching ratios reflect quantum interference effects.