Infrared Spectrum of a Molecular Ice Cube: The S_4 and D_(2d) Water Octamers in Benzene-(Water)_8

摘要

Resonant two-photon ionization, ultraviolet hole-burning, and resonant ion-dip infrared (RIDIR) speetroscopy were used to assign and characterize the hydrogen-bonding topology of two conformers of the benzene-(water)_8 cluster. In both clusters, the eight water molecules form a hydrogen-bonded cube to which benzene is surface-attached. Comparison of the RIDIR spectra with density functional theory calculations is used to assign the two (water)_8 structures in benzene-(water)_8 as cubic octamers of D_(2d) and S_4 symmetry, which differ in the configuration of the hydrogen bonds within the cube. OH stretch vibrational fundamentals near 3550 wave numbers provide unique spectral signatures for these "molecular ice cubes."