Time-Resolved Fluorescence Spectroscopy Using Pulsed Laser Excitation

Abstract

The technique of time-correlated single photon counting has been widely used during the past decade to study the time-dependent emission processes occurring in molecular species in the nanosecond time domain [l]. The time resolution and accuracy orthis method are largely dependent on the system stability and the confidence in deconvoluting the fluorescence decay from the finite instrument response. The most common excitation source employed for such studies is a spark discharge lamp which produces light pulses of a few nanoseconds duration but of rather variable pulse shape, low intensity and slow repetition rate. An apparatus has been developed in our laboratories incorporating photon counting detection methods but based on a mode locked, cavity dumped Spectra Physics 166/366 argon-ion laser excitation source which offers considerable advantages over existing time- resolved fluorescence techniques. The essential features of this instrument are illustrated in Fig.1.