VIBRATIONAL ENERGY DEPENDENCE OF THE ELECTRIC DIPOLE MOMENT OF WATER
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Date
2005
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
We present a detailed analysis of water dipole moments in highly vibrationally excited states. We use Stark Induced Photofragment Quantum Beat Spectroscopy to measure Stark splittings in vibrationally excited H$_2$O and HDO, and to obtain the projections of the dipole moment on the rotational inertia axes, $\mu_{a}$ and $\mu_{b}$, for 7 different vibrational states containing 4, 5 and 8 quanta of O-H stretching excitation}$ (2002), and 58$^\mathrm{th}$ (2003)}$^,$}, \textbf{297}, 993 (2002).\ \ \ P. Theule, A. Callegari, T. R. Rizzo and J. S. Muenter, \textit{J. Chem. Phys} \textbf{122(13)}, ppp (2005).}. These measurements, combined with earlier studies of $v=0$ and $v=1$ states, provide 22 individual dipole moment components in water molecules having vibrational energies extending over a range of 28\,000 cm$^{-1}$. To understand quantitatively the vibrational dependence of these moments and the origin of their change, we have developed a dipole moment model that accounts for the change of both molecular geometry and electronic charge distribution upon vibratonal excitation. In this model, the O$-$H bond vibration, where the great majority of the excitation is localized, is represented by a Morse oscillator wavefunction; the bond angle is treated parametrically and optimized for each state to reproduce experimental rotational constants; the dipole surface is based on the \textit{ab initio} calculations of Schwenke and Partridge}, 6592 (2000).}. Considerable care is required in the vibrational averaging process to produce calculated moments whose magnitude and orientation can be directly compared with experimental measurements. The results, which are accurate to a few percent, will be discussed in terms of general trends, including the relative importance of stretching vs. bending motions.
Description
{A. Callegari, P. Theule, T. R. Rizzo and J. S. Muenter, The Ohio State International Symposium on Molecular Spectroscopy, 57$^\mathrm{th{A. Callegari, P. Theule, J. S. Muenter, R. N. Tolchenov, N. Zobov, O. Polyanski, J. Tennyson, and T. R. Rizzo, \textit{Science{D. W. Schwenke, and H. Partridge, J. Chem. Phys., \textbf{113
Author Institution: Institut des sciences et ingenierie chimiques, Ecole; Polytechnique Federale de Lausanne, CH-1015 Lausanne,; Switzerland; Dept. of; Chemistry, University of Rochester, Rochester, NY 14627
Author Institution: Institut des sciences et ingenierie chimiques, Ecole; Polytechnique Federale de Lausanne, CH-1015 Lausanne,; Switzerland; Dept. of; Chemistry, University of Rochester, Rochester, NY 14627