The one-atom cage effect in I2(B)-Ar:: Evidence that caging is inefficient for the T-shaped isomer

Caged recombination is observed when the binary I(2)-Ar complex is excited to energies above the B state dissociation limit. The recombination mechanism 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, fluorescence depletion measurements were used to test these models. Fluorescence resulting from caged recombination could not be depleted using the well-known resonances of T-shaped I(2)-Ar. Instead, depletion via a diffuse band system previously assigned to the linear I(2)-Ar was observed. These results are consistent with the adiabatic recombination model. Geminate recombination of I(2) in a He supersonic expansion is also reported. (C) 1999 American Institute of Physics. [S0021-9606(99)01630-X].