Jet spectroscopy of p-methoxyaniline and intramolecular vibrational relaxation dynamics in the p-alkoxyaniline series

Abstract

The vibronic spectroscopy of p-methoxyaniline (p-anisidine) in the S1 and S0 states has been studied using laser induced fluorescence in a supersonic jet apparatus. The band origin is found at 31 581 cm−1. Vibrational modes 6a, 6b, 1, I, and 10b are found to be active in the excitation and emission spectrum and their frequencies are 395, 565, 821, 668(v=2), and 499(v=2) cm−1 in the excited state and 426, 642, 845, 472(v=2), and 525(v=2) cm−1 in the ground state, respectively. The intramolecular vibrational relaxation (IVR) dynamics discerned from the single vibronic level fluorescence (SVLF) spectra is compared with p-aminophenol and p-ethoxyaniline, the other two members of the p-alkoxyaniline series. It is postulated that the IVR dynamics in this series is dependent on the changes in the electronic structure in the excited state rather than the increase in the density of states alone.