Rigid cage photodissociation dynamics: A double minimum problem for ICl in Ne and Ar lattices

Excitation into the continuous visible absorption of ICl in Ne and Ar lattices produces both vibrationally relaxed BO+ and A 3π1 fluorescences. Photoselection studies show these emissions result from excitation of the BO+, and not the stronger 1π1, repulsive continuum. Negligible angular reorientation accompanies the photodissociation–recombination process, even for excitation 0.8 eV above the BO+ dissociation barrier. Normalized excitation spectra show that the deactivation process producing v=0 A 3π1 occurs only for excitation above the gas phase dissociation barrier. It is concluded that in the solid the avoided crossing between BO+ and CO+ is preserved, and that the observed dynamics reflect inclusion of an effective matrix potential to give a double minimum in the BO+ state.