Fluorescence dynamics spectrometer of single-picosecond resolution: Optimisation of experimental performance

Design and construction of a new spectrometer for picosecond fluorescence d ecay measurements by time-correlated single-photon counting is described. T he use of pico/femtosecond excitation pulses from a tunable Ti:Sapphire las er in combination with a fast microchannel plate photodetector and ultrafas t timing electronics resulted in an excellent temporal resolution and stabi lity of the instrument response function (IRF) of the spectrometer which en abled successful analysis of fluorescence decay signals of single picosecon ds. Results of optimisation of experimental characteristics of the system c oncerning the effect of the geometry of the excited region of the sample, o ptimum optical imaging and performance of photodetectors are presented. Tes t measurements of fluorescence decay of xanthione in various solvents chara cterised by different S-2 state lifetimes 5-38 ps proved the excellent expe rimental performance of the spectrometer.