Photoelectron spectroscopic and thermodynamic studies of the free surface of benzyl alcohol

He(I) photoelectron spectra of the liquid surface and the vapour of benzyl alcohol (C₆H₅CH₂OH) are reported. The gas-phase spectrum resembles that of benzene except that between the 1e_1g(π) and the 3e_2g benzenoid bands there is an additional peak in benzyl alcohol at 10.69 eV. In the spectrum of the liquid the additional peak is either absent or of much reduced intensity and this, together with consideration of the spectra of related molecules, leads to its assignment as the ionization of a “lone pair” orbital. In the condensed phase the lone pair electrons become involved in hydrogen bonding. Considerations of the excess energy and entropy of the surface of liquid benzyl alcohol point to a surface in which the hydrogen bonds are not broken, in agreement with the spectroscopic result.