Dispersed fluorescence spectroscopy of jet-cooled adenine

Abstract

Dispersed fluorescence spectra of jet-cooled adenine were obtained by exciting the vibronic bands observed in the fluorescence excitation spectrum from an earlier study (Kim et al., J. Chem. Phys., 2000, 113, 10 051). The dispersed fluorescence spectra reveal sufficiently well-resolved vibrational bands of the ground electronic state. The excitation of the C′ band at 36 062 cm−1 and the D′ band at 36 105 cm−1 results in emissions that are associated with out-of-plane and in-plane vibrational modes in the ground state, respectively, which suggests that these bands belong to different electronic states, as first proposed by us and later supported by others. A vibrational analysis yielded an assignment of the C′ band as an out-of-plane vibrational mode of the nπ* state and the D′ band as the 0–0 band of the ππ* state. Combination bands of the out-of-plane and in-plane vibrational modes are observed in the dispersed fluorescence spectrum of the C′ band, which seems to support that there is indeed a strong vibronic coupling between the nπ* and ππ* excited states of adenine.