Cerenkov radiation as a UV and visible light source for time-resolved fluorescence.
We demonstrate the first use of Cerenkov radiation for the measurement of fluorescence lifetimes. Relativistic beta particles from the nuclear decay of 90 Sr and 90Y generate a spectral continuum in a quartz waveguide. Light flashes of < 100-ps duration are delivered simultaneously to a sample cell and a reference photomultiplier. A simple, digitally based cross-correlation signal processor allows extraction of the sample fluorescence decay kinetics without distortions which can result from the random excitation pulse sequence. We characterize both the pulse duration and the pulse intensity of the light that is emitted from the waveguide. Although the excitation intensity is very weak, we demonstrate that accurate lifetime measurements are possible with only a few hundred seconds of integration time. Tests on a variety of compounds illustrate the utility of the light source throughout the UV and blue regions of the spectrum. We also discuss future design improvements and potential applications of this new approach to time-resolved fluorescence.