Reciprocal rates, electronically excited

The rate constant ke corresponds to the reciprocal of the lifetime of the excited state. Internal conversion The excited state can do other things, such as convert some of the original electronic excitation to a mixture of vibration and a different electronic state. These are also treated as unimolecular processes with associated rate constants ... 

Table 1.1 The lifetime, or reciprocal rates, in solution of photophysical processes involving electronically excited states (cf. Fig. 1.1)...

I" ", were interpreted as confirmation of the superexchange mechanism for reaction (1) [54]. This was further supported by the results obtained with 12", the free rotaxane, where photophysical properties very similar to I were evidenced, Scheme 1. The experimental kinetic data collected for these structures (Table 1) allowed us to derive a good correlation between the rates of electron transfer and the reciprocal of the energy gap between the relevant orbitals on the porphyrin excited state and on the phenanthroline ligand, confirming a superexchange mechanism for electron transfer, for reactions (1),... 

An adsorbed atom or a molecule being in its excited state is characterized by a finite lifetime which is determined by the reciprocal of the decay rate of this state. The finiteness of the lifetime leads to a broadening of the lines in the optical spectra of the adsorbate. Besides spontaneous emission which occurs also for free atoms and molecules, adsorbed species have other specific channels of relaxation, conditioned by their proximity to the surface. Any relaxation process must obey the conservation law of energy and therefore it takes place only if there is a substrate excitation which can accept the energy that the excited adsorbate releases. Therefore, possible decay mechanisms are determined by the energy spectrum of the substrate and thus generally are different for metals, semiconductors and dielectrics. They can be broadly classified as being mediated by photons, phonons, electron-hole pairs and conduction electrons. 

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