Fluorescence lifetimes of 9-methylanthracene in supersonic free jets. A level inversion between S1 and T2 states upon the phase change from solution to gas

Abstract

Synopsis. Fluorescence lifetimes measured for 9-meth-ylanthracene in supersonic free jets confirm the occurrence of nonradiative decay at the vibrationless level of S1 that has been suggested from the measurement of the fluorescence yield. The nonradiative decay constants in the isolated and condensed phases have been compared from the viewpoints of relative positions of S1 and T2 levels and of the magnitude of the energy gap.