| Popis: |
Recent experimental results from this laboratory have shown that fluorescence emission can be quenched by the light pulses from cavity-dumped dye lasers, a phenomenon we call `light quenching.' In this overview article we describe some of the possible effects of light quenching on the steady state and time-resolved spectral properties of fluorophores. The extent of light quenching was found to depend on the amplitude of the emission spectrum at the quenching wavelength. Different effects are expected and were observed for light quenching by a single laser beam (within a single laser pulse) or for a time-delayed quenching pulse. Light quenching can decrease or increase the time-zero anisotropy. Our calculations indicate that the anisotropies can increase to unity under selected conditions. Remarkably, the light quenching can break the usual z-axis symmetry of the excited state population, and the measured anisotropy (or polarization) depends upon whether the observation axis is parallel or perpendicular to the propagation direction of the light quenching beam. Quenching with time-delayed light pulses is predicted to result in oscillations in the frequency-domain intensity and anisotropy decays. A more complete description of `One and Two-Pulse Theory of Light Quenching,' is presented by Kusba et al. in this same volume. The predicted oscillations have been observed in frequency-domain intensity decay data. Overall, the results suggest a new class of two-pulse or multiple-pulse time-resolved experiments where the sample is prepared by the excitation pulse and subsequent modification of the excited state population by the quenching pulse(s), followed by time- or frequency-domain measurements of the resulting emission. |
