DETERMINATION OF EXCITED-STATE POTENTIAL-ENERGY SURFACES IN THE FRANCK-CONDON REGION FROM ELECTRONIC ABSORPTION-SPECTRA

A fast and efficient method using the first and second moments of the electronic absorption spectrum is described to determine the harmonic fit to the excited-state potential about the ground-state equilibrium configuration, i.e., the Franck-Condon region. It is an improvement over the conventional harmonic Franck-Condon analysis in the following ways. (a) It uses the minimum information to determine the harmonic fit to the excited-state potential in the Franck-Condon region. (b) It is easy to use, since it is not a fitting procedure. (c) It gives a definite sign to the shift in bond length. (d) It provides one bound to the actual shift in bond length. (e) It is computationally more efficient and gives accurate results. Examples of some diatomics and a polyatomic with separable modes are given to illustrate the method. © 1990 American Chemical Society.