# FOURIER TRANSFORM MICROWAVE SPECTRUM OF THE HYDROPHOBIC CLUSTER; PROPANE-WATER

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 Title: FOURIER TRANSFORM MICROWAVE SPECTRUM OF THE HYDROPHOBIC CLUSTER; PROPANE-WATER Creators: Steyert, D. W.; Suenram, R. D.; Lovas, F. J.; Saykally, R. J. Issue Date: 1992 Publisher: Ohio State University Abstract: The Fourier-transform microwave spectrum of the propane-water complex, $C_{3}H_{3}-H_{2}O$, has been observed and analyzed. This spectrum includes transitions assigned to propane complexed with both the ortho and para modifications of water. The rotational constants indicate that the vibrationally averaged structure has all four heavy atoms coplanar, with the water center-of-mass lying on or near the $C_{2}$ axis of propanc, inside the CCC angle, 3.76($\pm$.02) {\AA} from the propane center-of-mass, 4.35($\pm$.02) {\AA} from the methylene carbon. The projection of the dipole onto the a-inertial axis of the complex (0.732 Debye for the ortho state and 0.819 D for the para state) indicates that one of the protons of the water subunit lies on the $C_{2}$ axis of the propane subunit, the axis connecting the subunit centers-of-mass. The small projection of the dipole along the b-axis (0.14 D for the ortho state and 0.38 D for the para state) is most consistent with an equilibrium structure in which all three atoms of the water lie in the CCC plane of propane, with torsional tunneling about the hydrogen bond which is slow on the time-scale of the overall rotation. The small methyl-top tunneling splittings observed in the rotational spectrum of the propane monomer are not observed in the spectrum of the complex. Description: Author Institution: Department of Chemistry, Colgate University; Molecular Physics division, National Institute of Standards and Technology; Department of Chemistry, University of California URI: http://hdl.handle.net/1811/12743 Other Identifiers: 1992-RB-04