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

Design and construction of a new spectrometer for picosecond fluorescence decay measurements by time-correlated single-photon counting is described. The use of pico/femtosecond excitation pulses from a tunable Ti: Sapphire laser in combination with a fast microchannel plate photodetector and ultrafast timing electronics resulted in an excellent temporal resolution and stability of the instrument response function (IRF) of the spectrometer which enabled successful analysis of fluorescence decay signals of single picoseconds. Results of optimisation of experimental characteristics of the system concerning the effect of the geometry of the excited region of the sample, optimum optical imaging and performance of photodetectors are presented. Test measurements of fluores-cence decay of xanthione in various solvents characterised by different S(2) state lifetimes 5-38 ps proved the excellent experimental performance of the spectrometer .