The role of accepting modes in the theory of nonradiative transitions

✍ Scribed by Donald F. Heller; Karl F. Freed; William M. Gelbart

• Publisher: Elsevier Science
• Year: 1973
• Tongue: English
• Weight: 475 KB
• Volume: 23
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(73)89563-6

✦ Synopsis

we Ireat explicitly the role ofgeometry and frequency changes in the nonradiative decly of individual vibrational levels in isolated Iarge molecules, and present new results appropriate to the case of small effective energy gaps.

Recently, we presented

[ 1) a theory of the energy dependence of nonradiative decay rates in isolated large molecules, and applied it to the observed intersystem crossing rates from individual vibrational levels of the first excited singlet states in substituted benzenes [2]it. This approach has also been used by Yeung and Moore [3],

and by Porter et al.

[4], in treating their data on internal conversion in formaldehyde and naphthalene, respectively. Obviously, for each molecule of interest, detailed interpretations require that experimental conditions be such that hot bands (or other sources of spectral congestion) do not obscure the vibronic parentage of the prepared state. in our previous work, as well as in that of others IS], the following assumptions were made.

(i) The zero-order molecular states of interest can be characterized within the statistical limit*.

(ii) These vibronic states are reasonably well described within the adiabatic Born-Oppenheimer (ABO) approximation** _ (iii) Ali intramolecular interaction energies can be written as products of "electronic matrix elements" times "vibrational overlap" factors.

(iv) The normal modes are harmonic and parallel in the initial and final electronic states.