Spectroscopy and intramolecular vibrational redistribution in the S1 state of jet-cooled para-alkoxyanilines (NH2—C6H4—OCnH2n+1; n=4, 5, 6)

Abstract

Vibronic spectroscopy of the S1 and the S0 states of the higher members of the p-alkoxyaniline series, viz., p-butoxyaniline, p-pentyloxyaniline, and p-hexyloxyaniline was studied using laser induced fluorescence technique in supersonic jet expansion. All the compounds exhibited multiple band origins due to the presence of conformers and the strongest band origins for the S1�S0 transition were at 31543, 31549 and 31549 cm-1 for p-butoxyaniline, p-pentyloxyaniline, and p-hexyloxyaniline, respectively. Transitions in the vibrational modes 1, 9b, 6a, 6b, 10b, 11, 14, 16a, 16b and 7a were observed. Single vibronic level fluorescence spectra were recorded to obtain information on intramolecular vibrational redistribution (IVR) behavior in these molecules. The results from this work along with earlier observations on the first three members of the series give a complete picture of IVR behavior in this series. For the first three members IVR is governed by changes in the electronic structure in the excited state. For the rest of the series, IVR behavior scales with the density of states which is similar to that observed in other series reported in the literature. In the case of the p-butoxyaniline isomer dependent IVR was observed for the inversion excitation.