Excitation-emission study of continuum Raman and the photofragmentation mapping of IBr

Abstract

Experiments and theory of the excitation-frequency dependence of the continuum-Raman signal of IBr are described. The theoretical computations, which do not follow the Kramas–Heisenberg expression, are extremely successful in predicting the wavelength dependence of each Stokes line and the ratio between the different overtones. The ‘‘reflection principle’’ or ‘‘photofragmentation mapping’’ of absorption spectroscopy, which postulates the equivalence between the topology of an initial vibrational wave function and the frequency dependence of the cross section, is shown to hold also for continuum-Raman spectroscopy. Our experimental excitation–emission spectra for the low-lying overtones of IBr are a clear reflection of the final nuclear density. In contrast, we show that the excitation-frequency dependence of the high overtones is mainly sensitive to the shape of the intermediate excited electronic states.