Torsional splitting of the intermolecular vibrations of phenol (H2O)1 and its deuterated isotopomers

The intermolecular vibrations of phenol–water and their tunneling (torsional) splittings have been assigned in the S1 state by mass resolved spectral hole burning. The abundance of transitions in the low frequency region of the spectra can be traced back to torsional tunneling of the water moiety, which splits all vibronic levels. Especially the in plane wag vibration β2 exhibits a large splitting which points to a strong coupling with the H2O torsion τ and a substantial lowering of the effective torsional barrier after β2 excitation. Based on the discrimination of different isotopomers and their isomers and of the torsional sublevels a reassignment of some intermolecular transitions could be given.