Moment analyses of intensity distributions in molecular electronic spectra

Abstract

The use of moments in the analysis of vibronic intensity distributions in molecular electronic spectra is explored. Theoretical relations are derived for first moments. No attention need be paid to the form of individual vibrational overlap integrals. It is shown how these relations give information on the change of geometry accompanying the transition and on the dependence of the electronic transition moment on the appropriate normal coordinate. The theory is successfully applied to the 3500 AA emission spectrum of formaldehyde and to the 3400 AA spectrum of phenanthrene. An outline is given of the extension of the theory to higher moments.