Fluorescence decay, temperature dependence

If rate constants are competitive, we expect the emission of prompt fluorescence, phosphorescence and delayed fluorescence of energy quanta /7v/, h jp and //vn) respectively. Although //v/ is equal to ftvED, the lifetime of delayed fluorescence will match the lifetime of triplet decay. The rate constant ArEn for E-type delayed fluorescence is temperature dependent and can be expressed as... 

In addition, the quenching of the fluorescence of fluorophore groups in protein molecules by neighboring groups(35) and its temperature dependence, t36) energy transfer of electronic excitation and its dependence on excitation wavelength,(1) the type of emission decay kinetics,(1,2) and changes... 

S. P. Spragg and R. W. Wijnaendts van Resandt, The temperature dependence of the fluorescence decay of low-density lipoproteins, Biochim. Biophys. Acta 792, 84-91 (1984). 

A study on mechanistic aspects of di-ir-methane rearrangements has been published recently [72]. The kinetic modeling of temperature-dependent datasets from photoreactions of 1,3-diphenylpropene and several of its 3-substituted derivatives 127a-127d (structures 127 and 128) show that the singlet excited state decays via two inactivated processes, fluorescence and intersystem crossing, and two activated processes, trans-cis isomerization and phenyl-vinyl bridging. The latter activated process yields a biradical intermediate that partitions between forma-... 

Nardi and Yatsiv (141) studied the temperature dependence and the decay times of europium emissions in europium dibenzoylmethide. In this compound the ultraviolet radiation absorbed by the organic component is transferred to the rare-earth ion and fluorescence is emitted from two levels, namely, the SD0 and the 5DI. The compound was prepared by treating a solution of EuC13 in ethanol with a solution of dibenzoylmethane in ethanol. The compound was precipitated by the addition of piperidine. 

Another less-common form of unimolecular decay is also temperature dependent and results in the phenomenon known as is-type delayed fluorescence.183 For example, the lowest excited singlet and triplet states of eosin are quite close together in energy, so that excited... 

Fluorescence from the Do and Di levels of Eu3+ in doped SrTiOa (cubic perovskite structure) has been observed [618]. The fluorescence decay from the 5Di level consists of radiative transitions to the 7F states and a nonradiative dominant transition to the 5Do level. The decay of the 5X>o state is mainly radiative and is composed of both zero-phonon and phonon-assisted transitions, the latter accounting for much of the temperature dependence of its lifetime. For temperatures upto 300° K, the decrease in the sZ>o lifetime has been correlated [618] with the increased intensity of the vibronic bands [619]. Both 5Z>o 7Fi and 5Do 7F2 transitions as well as 5Di 7F, bD - 7F2 and 5Z>o - 7F show vibronic structures at room temperatures [619] and below. 

Flow does the occurrence of two fluorescing states for MK fit into the dynamic picture developed in Section IV The observed temperature dependence of the fluorescence quantum yield of MK in ethanol206 yields direct evidence that in this case, also, EBA < Ev. Recent time-resolved measurements at the Berlin Electron Storage Ring for Synchrotron Radiation (BESSY)207 support this argument The viscosity dependence of the decay of the short-wavelength fluorescence band in ethanol is consistent with an apparent value BA — 0.5Ev. Moreover, the decay is nonexponential, as would be expected for a barrierless relaxation. The lifetime of the TICT state (exponential decay) is 0.65 ns in acetonitrile at room temperature, that is, it is unusually short. 

Comparison of the time resolved data in several solvents for 28 with that for a similar molecule in which one of the quinones was replaced by a dimethoxyphenyl group showed an increase in the lifetime of the fluorescence decay, as would be expected from the removal of a second acceptor, as discussed above. However, the data are complicated by the fact that the decays of the dimethoxyphenyl analog were decidedly biexponential. This result was interpreted in terms of an orbital symmetry effect on the electron transfer reaction. Interesting solvent and temperature dependencies were also observed with 28. 

Figure 10.10 shows the interaction between TNS and the oq-acid glycoprotein. We notice that for a constant protein concentration, fluorescence intensity is higher at low temperatures. The 1increasing temperature (301 60,201 30, and 156 30, respectively, in arbitrarily scaled units), as expected from the known temperature dependence of nonradiative decay processes (Albani etal. 1995). 

The fluorescence of 0X1 in anilines is severely (ca. 10 times) quenched by ET, and, therefore, its dynamics reveal the ET dynamics. The temperature dependence of fluorescence decays of 0X1 in anilines is shown in Figure 4. The ultrafast single exponential decay (280 fs) of 0X1 in DMA does not show any temperature dependence from 280 K (7 °C) to 373 K (100 °C). In AN, however, a clear temperature dependence was observed in its non-exponential decay. As the temperature increases from 283 K (10 °C) to... 

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