Mass-analyzed threshold ionization of the trans-1-naphthol-water complex: Assignment of vibrational modes, ionization energy, and binding energy

Naphthol is a prototype example for the enhancement of the molecule-to-sol vent proton transfer after electronic excitation. In this work, we investigate the influence of water molecules attached to naphthol on the spectroscopic properties of the neutral excited-state S-1 and the ionic state. In addition to S-1<--S-0 spectra, we present mass-analyzed threshold ionization (MATI) spectra for 1-naphthol and for the first time of the 1-naphthol.H2O complex displaying a rich variety of intra- and intermolecular vibrational bands. The comparison of ionic spectra measured via different intermediate states allows us to assign various vibrational modes in the monomer and the 1-naphthol.H2O Cluster assuming a Deltanu = 0 propensity rule. Assignment is also based on the energies and atomic displacement patterns of vibrations calculated from ab initio theory.