SUPERSONICALLY COOLED MOLECULAR IONS IN A SLIT-JET DISCHARGE: HIGH-RESOLUTION INFRARED SPECTROSCOPY AND TUNNELING DYNAMICS OF HD$_2$O$^+$
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Date
2005
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Publisher
Ohio State University
Abstract
Jet-cooled high-resolution infrared spectra of partially deuterated hydronium ion, HD$_2$O$^+$ in the O-H stretch region ($\nu_3$ band) are obtained for the first time, exploiting the high ion densities, long absorption path lengths, and concentration modulation capabilities of the slit jet discharge spectrometer. Least-square analysis with a Watson asymmetric top Hamiltonian yields rovibrational constants and provides high level tests of ab initio molecular structure predictions. Transitions out of both lower ($\nu_3^{+}$ $\leftarrow$ 0$^{+}$) and upper ($\nu_3^{-}$ $\leftarrow$ 0$^{-}$) tunneling levels are observed, as well as transitions across the tunneling gap ($\nu_3^{-}$ $\leftarrow$ 0$^{+}$). The $\nu_3^{-}$ $\leftarrow$ 0$^{+}$ transitions in HD$_2$O$^{+}$ acquire oscillator strength by loss of C$_{3v}$ symmetry and permit both ground (27.0318(72) cm$^{-1}$) and excited state (17.7612(54) cm$^{-1}$) tunneling splittings to be determined to spectroscopic precision from a single rovibrational band. The splittings and band origins calculated with recent high level ab initio 6D potential surface predictions for H$_3$O$^{+}$ and isotopomers } } are in very encouraging agreement with the current experimental results.
Description
{X. C. Huang, S. Carter, and J. M. Bowman, J. Chem. Phys. 118 (12), 5431 (2003).{T. Rajamaki, A. Miani, and L. Halonen, J. Chem. Phys. 118 (24), 10929 (2003).
Author Institution: JILA, University of Colorado, Boulder, CO 80309
Author Institution: JILA, University of Colorado, Boulder, CO 80309