Energy transfer parameters

Let us consider ki as the rate ccmstaot of the excited state depopulation energy transfer mechanism, Ihc measured fluorcsccnec lifetime is thus equal to 

Energy transfer mechanism appears to affect fluorescence lifetime, mtensity and quantum yield. 

The distance R that separates the donor from the acceptor is calculated using equation 6.8  

The Forster distance Ro (in A) at which energy transfer efficiency is 50% is calculated with equation 2  

From the overlap of the fluorescence spectrum of the donor and the absorption spectrum of the acceptor, we can calculate the overlap integral J ( M cm ) 

Let us consider kt as the rate constant of the excited state depopulation via the energy-transfer mechanism the measured fluorescence lifetime is thus equal to 

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Berlman IB (1973) Energy transfer parameters of aromatic compounds. Academic, New York... 

Berlman I. D. (1973) Energy Transfer Parameters of Aromatic Compounds, Academic Press, New York. 

The ethyl radical decomposition is, effectively, at the low pressure limit under the PIMS conditions and the rate data were used, in conjunction with a master equation analysis, to obtain energy transfer parameters. This analysis is discussed further in Section 2.4.3. 

Berlman, I.B. In Energy Transfer Parameters of Aromatic Compounds Academic Press New York, 1973. 

Table 1, Energy transfer parameters for YVO4 with different activators...

The ratio kib/(kia+kib) has values of 3.5 xlO", 7.6 x 10" and 1.67 xlO for total N2/O2 diluent pressiues of 20, 50 and 100-700 Torr and 296 K, respectively. The simplest explanation of these observations is that the rate of reaction (lb) is close to its high-pressure limiting value for pressures above 100 Torr but in the fall off regime at pressmes of 50 Torr and below. It is likely that the pressure dependence reported herein for reaetion (lb) can be modelled using more conventional energy transfer parameters as Barker and Golden (2003) suggest. 

Tokmakoff, Payer and Dlott solved Eqs. (12) for shock up-pumping of naphthalene [51]. To solve Eqs. (12), the parameters needed are heat capacities which are easily determined from tables or from statistical mechanics, the energy transfer parameter k(V) and the initial phonon quasitemperature 0p(O). The timescale of the up-pumping process is essentially determined from the Hess and Prasad [139] low-temperature Raman measurements of the lineshapes of doorway vibrations at 175 and 212 cm, which gives t(0). Equation (13) can then be used to determine the value at ambient pressure k(Vo) = 2.7 J mopl-K ... 

TABLE 31 Lifetimes, and energy transfer parameters in microcrystalline samples of [MEuM(L42)3]" (M = Zn", Cr "), or their solution 1 mM in acetonitrile, under ligand excitation... 

Studies of vibrational relaxation using lasers have expanded dramatically in the past fourteen years due largely to the increased availability of versatile, high-power, pulsed-laser devices. Increased demand for energy-transfer parameters has resulted from attempts to develop new lasers and to push existing systems to their practical limits. Thus the development of lasers and the study of energy-transfer phenomena have been mutually synergistic processes. 

Estimation of collision parameters Lennard-Jones parameters for stable species can be estimated if their critical properties (Tc, V, Pd) and dipole moment are known (see, for example, the method by Brokaw [58], as described in Ref. [47]). For polyaromatic hydrocarbons, Wang and Frenklach [59] proposed a group contribution method for the prediction of Lennard Jones parameters. All these methods are restricted to stable molecules. To the best of our knowledge more general estimation methods, which are also applicable for radicals, are not available. The same is true for energy transfer parameters (—< aii) or < down>) Therefore, the common procedure is to identify a molecule of similar size or composition for which these data are available and use the same values for the species of interest. 

Berlman, I. B. (1973). Energy transfer parameters of aromatic molecules. Academic Press,... 

The previous sections demonstrated that reaction rates may be limited by intermolecular energy transfer at low pressure. As a consequence, transition-state theory overestimates the rate constant, and the appropriate expression for the rate constant should contain energy-transfer parameters and non-equilibrium factors. 

Table 1. Forster energy-transfer parameters calculated using steady-state spectroscopic measurements from solutions of BDHM and P2NMA in benzene.

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