Radiative probability

Table 6.3 Valuesof (a/ U a/) (reproduced with permission from Carnall et al., 1968) for the transitions departing from the F3/2 state. The values of Syj = /x 2/e and of the radiative probabilities A/j estimated for Nd YAG are also listed...

The following conclusion of the theory (1 ) is extremely important. The radiative transition 2 > Sq in a sandwich dimer is forbidden. In case of a dimer of 04 symmetry, the transition 2 (4Eg) > Sg (A g) is forbidden because of parity. There is no principle difference in the splitting nature of 2 and states for sandwich type dimers with lesser than D4h symmetry and the 2 > Sq transition remains quasi forbidden. This makes it possible to explain low P2 values obtained in (1 ) by a decrease of the 2 > Sg transition radiative probability, i.e., by decreasing or 2 > Sq fluorescence quantum yield in dimeric TTA complexes. In the case of non-sandwich dimer structures with location of subunits in one plane, the So state also is split into two states (high 202y and low 2B3g). However, two radiative transitions S2(B2y)... 

Radiative probabilities of T-S transitions have been presented by Hansen and Robinson [186] from absorption measurements of pure crystalline naphthalene. The 7 <— So... 

Donor acceptor charge transfer complex based photoreceptors continue to be described in the literature and studied using modern spectroscopic techniques but none has been commercialized. For example, the photoconducting charge transfer complex between poly(V-epoxypropylcarbazole) and TNF has been studied with transient absorption and time-resolved fluorescence. On the basis of Monte Carlo simulations, the results were interpreted in terms of a heterogeneity of charge transfer complexes with different radiative probabilities and a distribution of initial charge pair separation distances [30c]. 

The oscillator strength for the S j transition is almost independent of solvent (70,74,94), and It might thus be expected that the effect of solvent on the radiative probability would be slight. Cundall and Pereira (91,119) have reported measurements of kyfi in polar solvents, nonpolar solvents, and in particular perfluoro-n-hexane (in which solvent the similarity of... 

Under these conditions the singlet amplitude is distributed according to a Lorentzian distribution over the molecular eigenstates. Exciting with a broad (white) laser (or at least with a laser that completely spans the interaction width), one then sees in the fluorescence first the Fourier transform of the Lorentzian distribution, that is, an exponential decay. The density of /c> was, however, not taken to be so high as to dilute the singlet amplitude effectively to zero. It was taken to be intermediate, which meant that each ME still had enough radiative probability so as to radiate independently,... 

Fluorescence decay of 9-methylanthracene has been used by Tan and Treloar to study the coiling of poly(methacrylic acid) in water. Hara and Ware have studied the influence of solvent on the radiative probablity from the i state of pyrene. The fraction of fluorescence in the 0-0 parallels the extinction coefficient change for the 0-0 band. The Ham band also decreased with temperature, an effect correlated with the decrease in dielectric constant with temperature. There is also evidence that a solvent-solute interaction is involved in Ham band effects in alcohols and aromatic solvents. Use of the integrating sphere eliminates any uncertainty in the conventional instrumental refractive index correction. Some of the data obtained is given in Table 4. 

The lifetimes of the triplet-state sublevels of the mixed tris-cyclometalated Rh +-complexes, Rh(TTB)+, Rh(TPB)+, and Rh(PTB)+, were determined from optically detected microwave recovery and adiabatic rapid passage experiments performed at 1.4 K [66,75]. Typically, transients as displayed in Fig. 15 were obtained. The transients could be fitted in all cases to a bi-exponential of the form of Eq. (18). The ratio A/B equals the ratio of the radiative rate constants of the resonant sublevels. In Table 6 the resultant rate constants for the dopants Rh(TTB)+, Rh(TPB) and Rh(PTB)+ are collected. It is now obvious why for Rh(PTB)+ the 2 E zero-field ODMR transition could not be observed the and Ty sublevels have almost equal radiative probabilities. It is noted that the bi-... 

In the case of OH from the H -F O3 reaction, energy flux calculations were made assuming the collisional deactivation probabilities were proportional to the vibrational radiative probabilities. This model indicated that there was appreciable initial population of all vibrational levels with v 9. 

When changing the glass matrix, the radiative probabilities of R ions are less modified than the non-radiative ones. Consequently, the latter have to be considered first when optimizing a given ion-glass system. Although theories on non-radiative transitions are... 

The luminescence intensity of emission from a given level depends on the radiative and non-radiative probabilities. The quantum yields is expressed as... 

Fig. 21. a) Radiative and non-radiative processes dissipate energy competitively to bridge an energy difference or gap. The non-radiative processes require the emission of a number of phonons thus the non-radiative probability decreases as the number of phonons increases, b) Non-radiative decay rates plotted against the energy gap to the next lowest level for the excited states of various trivalent lanthanides in different hosts. The experimental gap law, eq. (10), is seen to apply. Hash marks denote the span of radiative decay rates encountered in these systems, thus if the non-radiative probability is below the hashed region fluorescence will be observed. After Riseberg and Weber (1976) and Imbusch and Kopelman (1981). 

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