Knowledge Bank

Mixed clusters of type $(C6H6)1-(H2O)n$ where n=3-8 (i.e., 1:n) have been studied using one-color resonance-enhanced two-photon ionization with time-of-flight mass spectrometric detection. The $S0-S1$ spectra obtained by monitoring the 1:2, 1:3, and 1:4 masses are remarkably similar in appearance. Several pieces of spectroscopic evidence will be presented that these clusters are forming tight, hydrogen-bonded networks of water molecules building off one face of the benzene ring, reflecting the immiscibility of the bulk liquids. Absorption features of higher clusters first shift further blue, and then rapidly to the red, with extensive van der Waals structure simultaneously appearing in the spectra. This general development is suggestive of the hydrogen bonded water network beginning to fold around the benzene molecule. Metastable ion studies using a reflectron TOFMS were also carried out on these clusters. For a given parent cluster, 1:n, metastable ion peaks were observed corresponding to loss of 1 to n water molecules.