Coupling synchrotron radiation with single photon counting and phase shift techniques for fluorescence lifetime measurements with picosecond resolution

Abstract

From the analysis of time and statistical properties of synchrotron radiation (SR) we derive the conclusion that the SR pulse has a gaussian shape whose width is wavelength-invariant from the far IR through the x-ray spectral region. This property highly simplifies the mathematical treatment of fluorescence decay experimental data obtained by single-photon-counting (SPC) using SR as a pulsed light source. The same considerations also allow us to consider SR as a precise intensity-modulated source of light making possible its coupling with phase-shift (PS) techniques to measure again fluorescence lifetimes. the main conclusion of this work is that SR can be simultaneously coupled with both SPC and PS techniques for the time-resolved spectrofluorometric experiment: with SPC one obtains the overall shape of the fluorescence decay reaching lifetime values with nanosecond resolution, and with PS we are able to approach to the lifetime values of shorter decays with picosecond resolution.