The lifetime of the fluorescent excited state in solid, liquid, and vapor phase cyclohexane

Abstract

The fluorescence lifetimes of cyclohexane in the solid, liquid, and vapor phase were measured using VUV synchrotron radiation from the National Synchrotron Light Source at BNL. The lifetime of liquid and solid cyclohexane changes with temperature, and the decay rate is a combination of a temperature-dependent Arrhenius-type process and a temperature-independent process. The results for liquid and solid cyclohexane from 59 to −49 °C can be represented by the expression 1/τ=[5.3×108+4.2×1012 exp(−5100/1.987 T)] s−1. The latest lifetime measurements available in the literature for cyclohexane are in good agreement with our values measured between 20 and 25 °C. The lifetime of liquid cyclohexane at a given temperature is independent of the excitation energy. However, in the vapor phase the lifetime strongly depends on the excitation energy.