COMBINED HIGH-RESOLUTION UV AND MICROWAVE RESULTS - STRUCTURE OF THE BENZONITRILE-WATER COMPLEX

High resolution ultraviolet (UV) and molecular beam Fourier transform microwave (MB FTMW) spectroscopy of the benzonitrile-water (BZNW) clus ter were performed to measure cluster structures in the S-0 and S-1 st ates. The MW experiments provide additional information on the structu re and the N-14-nuclear quadrupole coupling in the ground state S-0, t he UV experiments on the dynamics in S-1. The rotationally resolved su b-Doppler UV spectra of BZNW were measured by mass-selective resonance -enhanced two-photon ionization. For the first time this UV technique has been applied to hydrogen-bonded clusters. From the UV spectra the rotational constants are obtained by Correlation Automated Rotational Fitting. The MW spectra were analyzed with the model of a centrifugall y distorted rotor including nuclear quadrupole coupling. A r(0)-fit of the water position within the cluster is performed. The water is foun d to be located with its oxygen nearly in the plane of benzonitrile (B ZN). For S-0 (S-1), the distance of the oxygen to the ortho hydrogen i s r(0) = 2.477(4) Angstrom (2.457(2) Angstrom) and the angle to the or tho carbon-hydrogen bond 143.34(2)degrees (141.91(3)degrees). The stru cture differences in S-1 and S-0 can be explained by the structure cha nges of the BZN molecule. A line broadening, which points to a faster decay in S-1 upon clustering with the polar solvent, is observed for t he BZNW cluster.