Vibronic intensities in diatomic molecules

Abstract

AbstractThe object of this work is to use vibronic intensity distributions to determine the bond lengths of diatomic molecules in excited electronic states without having to evaluate Franck–Condon (FC) integrals. More specifically, the intent is to derive simple linear or quadratic expressions that provide good correspondence of bond lengths obtained from experimental vibronic intensity ratios with the experimental bond lengths. To that end, we will construct power‐series expressions for the FC integral in the harmonic approximation in terms of a parameter that approaches zero as the vibrational frequencies of the two combining electronic states approach equality, show how these expressions may be truncated, and evaluate the range of bond length changes over which the various approximate equations are valid. The study covered 60 different electronic transitions in 40 different diatomics. Of these, 40 electronic transition data sets were considered good enough to merit analysis. It will be shown that both approximations perform well within the limit of their applicability. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004