UPPER STATE FLUORESCENCE SPECTROSCOPY OF CENTROSYMMETRIC AROMATIC HYDROCARBONS

Abstract

Consecutive two--photon laser excitation has been extended to reveal new features of the ultraviolet fluorescence spectra of centrosymmetric aromatic hydrocarbons. The major differences of fluorescence spectra between centrosymmetric and non-centrosymmetric molecule can be classified into three different aspects: 1. molecular symmetry 2. excitation energy dependence of fluorescence structure 3. molecular relaxation We demonstrate results for two typical centrosymmetric molecules -- perylene and $(D_{2h})$ and 1,2,5,6, -- dibenzanthracene $(C_{2h})$ and a non-centrosymmetric molecule -- 3,4,9,10--dibenzpyrene $(C_{2v})$.