Inherent sample heating and temperature calibration in excited state absorption (ESA) measurements between room temperature and 77 kelvin

Abstract

Laser pulses of high intensities are usually required for recording excited state absorption (ESA) spectra of molecules in solution. Following the optical excitation non-radiative relaxation processes in the chromophores can lead to a remarkable and unintentional heating of the overall excited sample volume, especially at low temperatures. This temperature rise and its spatial distribution is investigated experimentally and compared to model calculations. The temperature of the excited sample volume was monitored by the temperature sensitive fluorescence of 4-methylumbelliferone (4-MU; synonymous with 7-hydroxy-4-methylcoumarine). A maximal temperature rise of several degrees was observed experimentally. Although the model was based on simple assumptions the agreement between theoretical results and experimental data proved to be satisfying.