Evaluation of the Radiationless Transition Probability

We now apply the formalism of Chapter 2 to calculate the nonradiative decay probability of statistical large molecules embedded in an inert medium. The basic ideas used to describe the transition probability follow logically from the following assumptions  

1) two-manifold electronic system is considered consisting of a limited number of 

2) Interference effects between resonances are neglected. It is thus assumed that the spacing between consecutive resonances centered about the energies Esm of the zero-order states considerably exceeds the widths of these resonances. 

3) The inert medium is characterized (with some exception) by the following features [92]  

4) As a further assumption, we adopt the so alled fast vibrational relaxation limit, according to which the vibrational relaxations in the excited electronic states are more efficient than electronic relaxations. Provided that vibrational relaxation rates considerably exceed the noru adiative decay probability, thermal equilibri- 

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