15min:

C. J. GRUENLOH, C. A. ARRINGTON, J. R. CARNEY, F. C. HAGEMEISTER AND T. S. ZWIER, Department of Chemistry, Purdue University, West Lafayette, IN 47907-1393; S. Y. FREDERICKS AND K. D. JORDAN, Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260.

One color R2PI-TOFMS, ultraviolet hole-burning, and RIDIRS have been used to assign and characterize the hydrogen-bonding topology of size-selected benzene-(H₂O)_n clusters formed in a supersonic molecular beam. Hole-burning spectroscopy confirms the presence of conformers in the increasingly congested R2PI spectra of these larger clusters. Two transitions in the benzene-(H₂O)₆⁺ R2PI-TOFMS are assigned to the benzene-(H₂O)₈ cluster. Comparison of the experimental RIDIR spectra to density functional theory calculations results in the assignment of these conformers to cubic octamers of S₄ and D_2d symmetry. The presence of benzene weakly distorts the cubic structures, breaking the degeneracy of several OH stretch vibrations and inducing intensity in otherwise forbidden infrared transitions. Four transitions in the benzene-(H₂O)₇⁺ R2PI-TOFMS are tentatively assigned as two conformers each of the (benzene)₂-(H₂O)₈ and the benzene-(H₂O)₉ clusters. The RIDIRS of these species share common features with those of the cubic benzene-(H₂O)₈ octamers; thus, a structure for the benzene-water nonamer built by adding one water molecule to a cubic octamer is tested against calculations.