Excited state intermolecular proton transfer in isolated clusters: 1-naphthol/ammonia and water

The excited singlet state intermolecular proton transfer reaction in jet-cooled clusters of 1-naphthol/ammonia and water is investigated employing mass resolved excitation, threshold photoionization, and emission spectroscopy. The complete data set indicates that no proton transfer occurs for 1-naphthol(NH3)1,2 and (H2O)n, n=1,...,20 clusters. Proton transfer occurs for (at least) one configuration of the 1-naphthol(NH3)3 cluster, as well as all 1-naphthol(NH3)n, n≥4, clusters. The (at least) two configurations of 1-naphthol(NH3)3 clusters are distinguished by threshold photoionization studies. The 1-naphthol(NH3)3 cluster for which proton transfer is indicated has a threshold photoionization energy ∼2000 cm−1 below the other 1-naphthol(NH3)3 cluster configurations. These results are employed to explain the previous discrepancy between static spectroscopic experiments and picosecond time resolved dynamic experiments concerning proton transfer in the 1-naphthol(NH3)3 cluster. Calculations of cluster geometry in 1-naphthol/ammonia and water cluster systems suggest some qualitative explanations of these observations.