Solvation of ion-pair states in nonpolar media: I2 in solid neon, argon and krypton

The ion-pair state emission spectra of I2 isolated in Ne, Ar, and Kr matrixes at 300-700 nm and vacuum UV spectra at 50,000-60,000 cm-1 are presented. Spectroscopic anal. of the UV and visible emission bands of the lowest-lying ion-pair state D'(2g) in Ne and Ar provides unambiguous evidence for both vertical (energy) and horizontal shifts (equil. distance) due to solvation in a rare gas matrix, and suggests that the ion-pair states maintain their distinct character. In Kr the previously reported broad emission band at 420 nm consists of 2 narrow bands, which have counterparts in the visible. They are assigned to emission from D'(2g) and a 2nd ion-pair states of I2, most probably the d(2u) state. Partial charge delocalization to the matrix can only play a minor role in Kr since similar emission is found for secondary sites in Ar. These findings should be highly relevant for a description of ion-pair states in nonpolar media. They are useful for the interpretation of time-resolved expts. that use the ion-pair state emission as probe signal. [on SciFinder (R)]