Time-gated Fluorescence Spectroscopy of Photoreceptor Pigments
Time-resolved fluorescence spectroscopy using ultrashort pulsed lasers as the excitation source has found a wide number of applications both in photochemistry and photobiology (Schneckenburger et al., 1988). In fact, the most common techniques based on continuous wave (cw) measurements are inadequate whenever the fluorescent signal is very low and/or cannot be separated from the background by spectral discrimination (i.e., by a suitable choice of the excitation or observation wavelength). Different fluorophores, however, even when overlapped in spectra, usually appreciably differ in their fluorescence decays and their presence can be detected by measurements in the time domain. Moreover, the decay time of the fluorescence emission is a parameter very sensitive to the molecular environment and its variations can provide useful information on the photophysical properties of the chromophore. If the time-resolved fluorescence analysis is performed at different wavelengths, it is also possible to obtain time-resolved spectra, by measuring the fluorescence intensity at given time intervals with respect to the peak of the waveform. By choosing suitable time gates, the spectral characteristics of the molecular species with slow decay time constants can be discriminated with respect to the fast ones and this information allows an accurate characterization of the emitting molecular species that are present in the sample.
KeywordsFluorescence Decay Exponential Component High Pulse Repetition Rate Pulse Picker Gated Spectrum
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