The one-atom cage effect in I-2(B)-Ar: Evidence that caging is inefficientfor the T-shaped isomer

Caged recombination is observed when the binary I-2-Ar complex is excited t o energies above the B state dissociation limit. The recombination mechanis m has been the subject of several previous investigations. Two alternative models have been proposed; Nonadiabatic recombination in a T-shaped complex , or adiabatic recombination in linear I-2-Ar. In the present study, fluore scence depletion measurements were used to test these models. Fluorescence resulting from caged recombination could not be depleted using the well-kno wn resonances of T-shaped I-2-Ar. Instead, depletion via a diffuse band sys tem previously assigned to the linear I-2-Ar was observed. These results ar e consistent with the adiabatic recombination model. Geminate recombination of I-2 in a He supersonic expansion is also reported. (C) 1999 American In stitute of Physics. [S0021-9606(99)01630-X].