Electronic spectra of jet-cooled 5-phenyltropolone. The effect of excitation of the torsional vibrational levels on proton tunneling

Abstract The S 1 -S 0 fluorescence excitation and dispersed fluorescence spectra of jet-cooled 5-phenyltropolone were measured to investigate the effect of the excitation of the torsional motion around the bond joining the phenyl group and the seven-membered ring in the S 1 state. The tunneling splitting of the origin band of 5-phenyltropolone (18 cm −1 ) is only slightl smaller than that tr tropolone (18.9 cm −1 ), while the torsional excitation remarkably decreases the tunneling splitting.