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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 $(D2h)$ and 1,2,5,6, -- dibenzanthracene $(C2h)$ and a non-centrosymmetric molecule -- 3,4,9,10--dibenzpyrene $(C2v)$.