Spectral-polarization characteristics of the luminescence of solutions of organic molecules under light-quenching conditions. The quenching mechanism

Воропай, Е. С.; Gaisenok, V. A.; Kirsanov, A. A.; Саечников, В. А.; Sarzhevskii, A. M.

doi:10.1007/bf00666703

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“…Upon illumination on the long-wavelength side of the emission of DCS, we observed a shift of the emission spectra to shorter wavelengths. Spectral shifts due to light quenching have been reported for the phthalimide probes in pioneering studies by several Russian spectroscopies. − However, these measurements relied on the use of intense pulses from Q-switch ruby lasers. To the best of our knowledge, spectral shifts due to light quenching have not been reported using modern high repetition rate lasers, and there have been no studies of the effects of the delay time t d on the emission spectra.…”

Section: Introductionmentioning

confidence: 99%

Effect of Fluorescence Quenching by Stimulated Emission on the Spectral Properties of a Solvent-Sensitive Fluorophore

et al. 1996

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We examined the emission spectra and wavelength-dependent anisotropies of the solvent-sensitive fluorophore 4-(dimethylamino)-4′-cyanostilbene (DCS) under condition of fluorescence quenching by stimulated emission. The sample was illuminated with a train of 10 ps pulses at 285 nm, and a train of stimulating pulses at 570 nm which were delayed by a time t d relative to the excitation. Stimulated emission of DCS was demonstrated to occur by observation of gain in the long-wavelength beam. Illumination on the long-wavelength side of the emission spectrum with the long-wavelength time-delayed pulses resulted in a blue shift of the emission spectrum, and a progressive decrease of the emission anisotropy as the observation wavelength increased toward the stimulating wavelength. The spectral shifts and wavelength-dependent anisotropies of DCS were more pronounced in more viscous solvents where spectral relaxation is incomplete during the excited state lifetime. Light quenching of DCS in a low-viscosity solvent revealed no spectral shifts or wavelengthdependent anisotropies. Control measurements using acridine orange, which is relatively insensitive to solvent polarity, did not show any spectral shift or wavelength-dependent anisotropy with light quenching. The data for DCS can be explained by the presence of a time-dependent spectral shift and wavelength-selective quenching of the longer wavelength emission. In this model the relaxed state is formed following excitation of the unrelaxed state, and the relaxed state is preferentially quenched by long-wavelength illumination. Comparison of the data with model calculations indicates the presence of at least two spectral relaxation times. These results demonstrate that light quenching by stimulated emission acts selectively based on overlap of the stimulating wavelength with the emission spectrum. Observation of the emission spectrum in the presence of time-delayed and power-controlled long-wavelength pulses can be used to study time-dependent excited state processes.

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Section: Introductionmentioning

confidence: 99%