Radiative relaxation for

Turning to the fully quantum mechanical approach, we find that the lowest order rate theory for general non-radiative relaxation processes also provides a factorized rate expression ... 

Figure 5. Rate-energy curves for benzene ion dissociation. Circles are TRPD points (corrected for IR-radiative relaxation) from Ref. 24 squares are REMPI points from Ref. 10. The two points with ( ) symbols are TRPD points uncorrected for radiative relaxation. The curves are from variational RRKM, with Eq = 3.88 eV, and simple RRKM, with Eo = 3.81 eV.

Phosphorescence corresponds to a different relaxation process. After the absorption phase, corresponding to the transfer of one electron into the Si level (singlet state), a spin inversion can occur if vibrational relaxation is slow, leading the electron to a T, state (triplet state) that is slightly more stable. Flence, return to the ground electronic state will be slower because it involves another spin inversion for this electron. For this reason, radiative lifetimes for phosphorescence can be up to 108 times greater than for fluorescence. 

One further case should be examined. Suppose that in equation (9), Q is formed and is chemically reactive, going to product P with a rate constant k CT. In addition, Q will have rate constants k nr and k r for nonradiative and radiative relaxation, respectively. The situation is now that light is absorbed by A, but we measure the formation of product P. We speak of such a process as one of sensitization, that is, the formation of P is photosensitized by A. 

After extraction, the fluorescent indicator was in the unbound state and gave input to the radiative relaxation. Therefore, the fluorescence lifetime increased and, consequently, the intensity as well. After MIP contacting with the analyte, the non-radiative processes were again efficient compared to the radiative processes and, subsequently, fluorescence was quenched. With steady-state fluorescence spectroscopy the cross-reactivity test towards structurally similar biomolecules was performed that yielded selectivity factors for guanosine, cAMP and cCMP of 1.5, 2.5 and 5.1, respectively. 

DFT calculations on the model compound Cu6I6(SPhCH3)6 in its triplet state predict that the SHOMO localizes the spin density mainly on one Cu atom and its three iodo neighbors with the rest on one -SPh fragment, whereas it is rather delocalized over the Cu and I atoms in the HOMO (Fig. 32). The SHOMO is located at -0.042 a.u. above the HOMO (-0.125 a.u.). The simple arithmetic difference between the two levels suggests that the radiative relaxation should occur in the vicinity of 550 nm, which fits the experimentally observed maxima (Fig. 31). So the first theoretical study confirms a cluster-centered excited state as responsible for the observed emission, similar to other Cu4I4-containing species.146... 

The energy stored in an excited state is dissipated by the unimolecular radiative and radiationless relaxations. For strongly allowed electronic transitions, Strickler and Berg have obtained an expression for the rate constant of the excited-state radiative decay (Equation 6.67).31... 

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