Fluorescence temperature sensing based on thermally activated singlet-triplet intersystem crossing in crystalline anthracene

Abstract

The temperature dependence of a steady-state fluorescence spectrum of anthracene crystals ranging from 300 K to 500 K had been investigated, which was in the temperature range of most tabletop laser driven shock wave experiments. An interesting finding is that the fluorescence intensity of the 2-0 transition increases more rapidly than other transitions as the temperature increases. In particular, the logarithm of intensity ratios γn shows a linear correlation with inverse temperature, which can be used for fluorescence temperature sensing. The analysis of sensitivity η and random uncertainty ΔT has demonstrated that the intensity ratio γ1 is the best comprehensive performance physical quantity for temperature sensing. Theoretical analysis and experimental results demonstrated that the unusual increase in the intensity of 2-0 transition originated from a second excited triplet state T2, which was thermally coupled with the first excited singlet state S1. In a word, we established a new fluorescence temperature sensing method based on the intensity ratio and clarified that the mechanism of this method was the thermally activated singlet-triplet intersystem crossing.