MICROWAVE OBSERVATION OF THE OH-H$_2$O RADICAL COMPLEX

Author Institution: Department of Chemistry, University of Minnesota, Minneapolis,; MN 55455; Department of Chemistry, Amherst College, Amherst, MA 01002-5000The radical complex OH-H$_2$O has been observed by rotational spectroscopy. Spectra for $^1$$^6$OH-$^1$$^6$OH$_2$O and $^1$$^8$OH-$^1$$^8$OH$_2$ have been analyzed using a two-state model which accounts for nuclear motion on both the $^2$A$^\prime$ and $^2$A$^{\prime\prime}$ potential surfaces. Partial quenching of the OH orbital angular momentum dramatically affects the rotational spectra, and the $^2$A$^\prime$-$^2$A$^{\prime\prime}$ energy separation, $\rho$, is determined to be -146.50744(42) \wn. The ground state of the complex has approximately 86{\%} $^2$A$^\prime$ character and the vibrationally averaged OH-OH$_2$ hydrogen bond distance is 1.952 \AA. The magnetic hyperfine constants for the OH proton in the complex are significantly altered from monomer values