VIBRATION-ROTATION SPECTROSCOPY OF THE HYDRATED HYDRONIUM IONS $H_{5}$$O_{2}^{+}$ AND $H_{g}$$O_{4+}$
Loading...
Date
1992
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
This paper reports on the partially successful $attempt^{1}$ to obtain high-resolution spectra for $H_{5}$$O_{2}^{+}$ and $H_{9}O_{4}^{+}$, whose vibrational spectra have been reported $previously^{1,2}$. These cluster ions are produced in a corona discharge ion source using 200 Torr of $H_{2}$ and trace quantities of $H_{2}O$. Following supersonic expansion and skimming, the ion beam is focussed, mass selected, and trapped in an octopole ion trap. After spectroscopic interrogation using a two-color laser scheme, the trapped ions are released and fragment ions are counted using standard ion counting methods. The two-color laser scheme used a tunable Burleigh cw F-center laser with an intracavity etalon for initial excitation of the ions, and an MPB Technologies Inc. cw $CO_{2}$ laser to preferentially dissociate the vibrationally excited ions via a multiphoton process. High resolution spectra for $H_{5}$$O_{2}^{+}$ were recorded in the antisymmetric OH stretching region near $3700 cm^{-1}$. Many more features were observed than could be explained if the molecule were rigid, and we have assumed that many of these additional features arise from tunneling spittings associated with large-amplitude internal motions in this cluster ion. Theoretically expected splitting patterns were calculated using a formalism developed earlier for tunneling motions in hydrazine, since $H_{2}N-NH_{2}$ and $H_{20}-H^{+}-OH_{2}$ are group-theoretically similar if the central proton of the ion is located symmetrically between the two water molecules. We also attempted to compare these theoretical expectations with the experimental observations. Despite the low signal levels, we were able to group all the observed spectral features into roughly twelve series of lines. Intensity information, however, was not reliable, which prevented us from arriving at an unambiguous spectral analysis. We shall finally discuss now experimental data which could help in making further progress.
Description
$^{1}$ L. I. Yeh, Ph.D. Thesis, University of California, Berkeley, 1988. $^{2}$ L. I. Yeh, M. Okumura, J.D. Myers, J.M. Price and Y. T. Lee, J. Chem Phys. 91 , 7319, (1989).
Author Institution: Exxon Research and Engineering Co.; Department of Chemistry, University of California; Molecular Physics Division, National Institute of Standards and Technology
Author Institution: Exxon Research and Engineering Co.; Department of Chemistry, University of California; Molecular Physics Division, National Institute of Standards and Technology