Photoelectron Ejection and Fluorescence from Molecular “Rydberg” States in Polar Solvents

Abstract

Abstract Absorption and fluorescence spectra and photo-current yield curves of tetraaminoethylenes are studied. The UV absorption of these compounds is mostly attributable to the transitions from the ground state to the “vertical” Rydberg-like and ionized states. Their spectral shapes in ether and in pentane are nearly coincident with each other, showing that these states just after excitation are little affected by the solvent polarity. Based on this result and the results of photo-current measurements, the spontaneous formation of free, solvated electrons from the “vertical” Rydberg-like states in polar solvents has been verified. It is also found that the maximum wave numbers, the lifetimes and the yields of the fluorescence from the lowest “relaxed” Rydberg-like state depend strongly on solvent polarity, temperature and rigidity. These results are explained by taking account of the competition between electron ejection and relaxation processes and of the presence of a non-fluorescent, solvated cation-electron pair. The photo-electron ejection from other organic molecules in polar solvents reported before is shown to be explained by the same scheme as presented here.