Laser-induced fluorescence spectroscopy of jet cooled p-aminophenol

The laser-induced fluorescence spectra of p-aminophenol both in excitation and emission have been studied in a supersonic jet apparatus. The characterization of the observed spectra was done by comparison with other related substituted anilines and the IR data available in the literature. The excitation spectrum resembles that of aniline with optical activity mainly confined to 6a, 1, and the NH2 inversion mode. In addition, the C–X in-plane bending mode 9b was also found to be optically active. The 6a mode dominates in most of the dispersed fluorescence spectra and shows a strong Franck–Condon activity. Unlike other similar molecules, the Δv=0 transitions were weak in the single vibronic level fluorescence spectra of 6a1 and 11, which has been qualitatively explained in terms of Franck–Condon analysis. The onset of intramolecular vibrational redistribution occurs at 1135 cm−1, which is much higher than many substituted anilines. The van der Waals complexes viz. p-aminophenol–Ar1 and p-aminophenol–Ar2 were observed. A symmetric (1|1) complex for the p-aminophenol–Ar2 is proposed based on the redshift additivity.