Excited lifetime

Figure 7-27 shows the frequency dependency of the in-phase PA bands in a-6T, measured at the maxima of the various PA bands. As expected, the two polaron bands are correlated with one another, having virtually the same dynamics. In contrast, the bipolaron PA band at 1.1 eV is virtually flat from 10 to 1000 Hz, indicating that trapped pol is are longer lived than trapped bipolarons in -6T. The excitation lifetimes modeled by comparing the data in Figure 7-27 to... 

Distinguish between the excited lifetime and radiative lifetime of Si and Ti states. 

The aF3,2- 4F5,2 emission of Nd3+ at 885 nm can also be monitored in a rather similar way, and a study of emission lifetimes together with absorption spectra for the hypersensitive Nd3+ transitions, e.g. %/2- 4Gs/2, has been made in order to investigate the solvation of neodymium nitrate and perchlorate in MeCN, Me2CO, DMSO or DMF. Excited lifetimes varied from 300 ns in Me2CO to 2300 ns in CD3CN. It was found that species Nd(N03) (3 ")+ were formed, where n = 1-5, on addition of NOJ ions to perchlorate solutions, but that addition of DMSO to Nd(CI04)3 in MeCN gave [Nd(DMSO) ]3+, where n = 9.7 0.8.618... 

Absolute quantum yields measured upon ligand excitation, lifetimes (standard deviation in parentheses), and associated hydration numbers of the Lnm podates with Hg91, 6.5 x 10 5 M in aqueous solutions at 295 K and pH 7.4. 

Qualitatively the same is true also for the non-Markovian Stern-Vomer constant for the irreversible quenching represented by Ko from Eq. (3.27), but the plateau that cuts the FEG parabola is shifted up more, the shorter the excitation lifetime x. The qualitative confirmation of the diffusional nature of the plateau was obtained experimentally in Ref. 89, where the true kinetic constant ko(AGi) was measured as the initial value of the time-dependent rate constant (3.37). The latter roughly follows the expected FEG dependence (Fig. 3.14), as it is essentially larger than k0 in the activationless region (—AG where... 

The initial charge distributions, which were recognized as very important, were analyzed in more detail in a number of works [32]. The analysis was extended to multichannel ionization [179], and the role of the excitation lifetime was specified [25]. A few articles devoted to them were published by Murata and Tachiya [26,27]. Earlier these authors studied experimentally the non-stationary kinetics of fluorescence quenching, which was fitted numerically... 

Unlike standard Markovian rate constants these constants depend on the excitation lifetime and light intensity. Using them, we can obtain a set of algebraic equations for the stationary concentrations of reactants and reaction products passing to the limit t —> 00 in Eqs. (3.505) ... 

Figure 3.99. The normalized distribution of ions produced by the biexcitonic ionization, according to Markovian theory (thick line) and non-Markovian UT distributions at different excitation lifetimes (dashed lines) (1)td = 1()6 ns, (2) zD — 100ns,(3)td — 10 ns. (From Ref. 275.)...

However, above the CMC, biexponential lifetime profiles and enhanced emission quantum yields are observed for both complexes. Comparison with the excited lifetime of the parental complexes showed that the longer component can be assigned to the aggregated species. Such findings could be explained in terms of smaller nonradiative rate constant, as consequence of... 

As noted above (Section II), rhenium(I) complexes have relatively long excitation lifetimes in solution at room temperature and can be used as redox photosensitizers that drive... 

Photolysis of C3O2 at 193 nm shown to produce C2 514 Swan band emission in addition to C2O, in contrast to behaviour observed following 248 nm excitation. Lifetime studies indicate that the Cj may be formed in secondary processes... 

With few exceptions, the fluorescence excitation spectrum of a single fluorophore in dilute solution is identical to its absorption spectrum. Under the same conditions, fluorescence emission spectrum is independent of the excitation wavelength, due to the partial dissipation of the excitation energy during the excited lifetime. The emission intensity is proportional to the amplitude of the fluorescence excitation spectrum at the excitation wavelength. 

DJ Lundell, RC Williams and AN Glazer (1981) Molecular architecture of a light-harvesting antenna. In vitro assembly of the rod substructures of Synechococcus 6301 phycobilisomes. J Biol Chem 256 3580-3592 S Brody and E Rabinowitch (1957) Excitation lifetime of photosynthetic pigments. Science 125 555 G Tomita and E Rabinowitch (1962) Excitation energy transfer between pigments in photosynthetic cells. Biophys J 2 483-499... 

Another feature of the phase-resolved method is that contributions for individual fluorophores can be examined if there is adequate separation in the different fluorescence excited lifetimes. When there are n fluorescent species present, the resulting signal from the lock-in amplifier... 

What we can conclude is that the luminescence process involving a phosphor is indeed complicated and is a dynamic process in which the excited center undergoes many perturbations by the lattice during its excited lifetime. 

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