INFRARED-SPECTRUM OF A MOLECULAR ICE CUBE - THE S-4 AND D-2D WATER OCTAMERS IN BENZENE-(WATER)(8)

Resonant two-photon ionization, ultraviolet hole-burning, and resonant ion-dip infrared (RIDIR) spectroscopy were used to assign and charact erize 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 us ed to assign the two (water), structures in benzene-(water)(8) as cubi c octamers of D-2d and S-4 symmetry, which differ in the configuration of the hydrogen bonds within the cube. OH stretch vibrational fundame ntals near 3550 wave numbers provide unique spectral signatures for th ese ''molecular ice cubes.''