Supersonic jet spectroscopic study of p-methoxybenzyl alcohol

Abstract

Fluorescence and mass-resolved S-1-S-0 excitation spectra of p-methoxybenzyl alcohol in a supersonic jet are reported. The long vibrational progression bands are observed in both spectra and attributed to the modes involving torsional motion of the CH2OH moiety with respect to the rest of the molecule. The spectral origin for the S-1-S-0 transition is found to be at 35 701 cm(-1). Two additional distinct vibrational progression bands are observed with their pseudo origins at 35 785 and 35 863 cm(-1). Fluorescence depletion spectroscopy shows that these three vibrational progression bands are originated not from three different conformers but From single conformer in the jet. The torsional barrier height of 316 cm(-1) in the S-1 ground-vibrational state is obtained from the comparison of the experiment with the calculation assuming a sinusoidal function for the potential energy surface along the torsional angle. The comparison of the relative intensity distributions in the vibrational progression bands with the calculation of Franck-Condon factors using a free-rotor basis set suggests that the molecular geometry at the minimum energy of the Si state is around 45 degrees rotated about the CH3OC6H4-CH2OH axis compared to that of the S-0 state.