Radiative constant

In tliese equations and are tire excited state populations of tire donor and acceptor molecules and and are tire lifetimes of tire donor and acceptor molecules in tire excited state tire notation is used to distinguish it from tire radiative constant (in otlier words for tire donor) is given by (C3.4.5) and tire... 

The oscillator strength of the longest wavelength absorption band of BMPC (1.1, [25]) is very similar to those of two previously studied carbocyanines (DOC and DTC) [45] so that we can expect that, for BMPC as well as for EK)C and DTC, the radiative constant (kp) is equal to 2-3x10 s". Combining this value with the fluorescence quantum yield of BMPC in methanol, 4)p= 5.3x10", we can estimate its room-temperarnre fluorescence lifetime to be = 2 ps. 

The measured absorption coefficient of hexagonal GaN at the excitonic gap ranges from 3 x 104 [41] to 1.5 x 105 cm 1 [36,42], From this last value, a value for the radiative constant B of 1.1 x 10 8 cm3/s can be derived [42], This is more than one decade higher than in GaAs. 

In this expression, the observed decay constants are assumed to be radiative, i.e., the quantum yield of the phos phorescence is assumed to be unity. Later other expressions were given using PMDR methods, from which the ratios of the radiative constants may be determined (27). 

In these equations and are the excited state populations of the donor and acceptor molecules- and and are the lifetimes of the donor and acceptor molecules in the excited state the notation x° is used to distinguish it from the radiative constant x° (in other words x° = Xg, for the donor) is given by (C3.4.5I and A the corresponding rate constant for the backward energy transfer from acceptors to donors can be foimd by me same means. Finally, and represent external sources of excitation, for example the absorption of laser light by the donor and acceptor molecules. Commonly, for example in the case of 8-pulse excitation (in practice an ultrashort laser pulse), (C3.4.6) yields exponential decay kinetics for p(f) and n t). The opposite case of steady excitation (CW light), yields the equilibrium ratio... 

Physical choices of the exit rates and the radiative constants equivalence of different models. The choice of the exit rates in the discrete site method and the k s in the radiation boundary method depends on the physical problem under consideration. For channel transport, they can be determined from the coupling of the quasi one-dimensional diffusion inside the channel to the three dimensional diffusion outside. This can be performed either in the forward [79] or the backward [89] formalism and results in A = in the radiation boundary condition method... 

Multi-exponential decays can also be observed from a single luminescent compound. For example, the compound under examination can be present in two (or even more) different chemical environments (e.g., due to different solvent shielding), producing species with different lifetimes. Normally the radiative constant of a luminescent species is independent of the chemical environment, and in such a case the pre-exponential factors are related to the fraction of species experiencing different environments. In biochemical research it is very common to consider that a multiexponential decay can result from different conformers of a single biological molecule. 

Spin selective information on the lowest triplet state decay was obtained by optical detection of magnetic resonance transitions between the spin components of the T state of FBP in n-octane. Because of the absence of phosphorescence at these conditions, the ODMR signals were detected via changes in the 5i->5o fluorescent intensity [6, 29], Our calculations reproduce the fluorescent frequency and radiative constant rather well. In order to complete the interpretation of the microwave-induced fluorescent ODMR measurements [6, 29] one has to calculate the zero-field splitting in the T state and hyperflne coupling between electron and nuclear spins. 

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