Molecular Structure from Rotational and Vibrational Transitions in Electronic Spectra

Abstract

Molecular structural information from rotational transitions in electronic spectra is derived from the rotational constants A, B, and C in the corresponding electronic state. The results of various techniques, from rotational band contour analysis of room temperature absorption spectra to line-by-line analysis of very high resolution supersonic jet fluorescence excitation or multiphoton Ionisation spectra, are discussed, as applied to the So and Si electronic states of fairly large molecules. Structural information from vibrational transitions in electronic spectra of such molecules results from the observation, in the ground or an excited electronic state, of as many levels as possible of large amplitude vibrational motions such as inversion, torsion or ring-puckering. These levels are then fitted to a model potential and the structure, corresponding to a minimum in the potential energy for that coordinate, obtained.