Microscopic solvent effects on the S 1T 2 intersystem crossing of 9,10-diphenylanthracene in supersonic free jets

Abstract

Fluorescence excitation spectra and fluorescence decays were measured for isolated 9,10-diphenylanthracene (DPA) and its van der Waals (vdW) complexes with Ar and Xe atoms. The fluorescence lifetime of DPA at the S 1 origin is significantly shorter than the pure radiative lifetime. In contrast to the condensed phase, intersystem crossing from S 1 to T 2 occurs in the isolated state because S 1 is located above T 2 in the absence of solvation. It is proposed that S 1 lies below T 2 when the number of Xe atoms coordinated to DPA is increased, since the heavy-atom effect of Xe on the fluorescence lifetime, which is observed for the 1:1 vdW complex, disappears in the highly coordinated complexes.