Knowledge Bank

The $v2=2++1-$ vibrational spectrum in $H3O+$ has been detected at wavelengths between $15\mu m$ and $22\mu m$ by diode laser absorption spectroscopy. The ion was generated in a glow discharge in a mixture of hydrogen and oxygen. The successful assignment of the spectrum depended to a large extent on the availability of reliable theoretical estimates of the band origin and structure since even the strongest lines are comparatively weak and lie in a crowded part of the oxonium ion spectrum. The band origin was found to be at $521.4cm-1$ which compares well with the most recent $prediction1$ based on extrapolation from previously observed lower lying levels. The $2+$ level, by analogy with ammonia, is expected to be perturbed by the $v4=1$ level and we find that it is not possible to fit the observed rotational structure to within the expected precision using the standard symmetric top formulae. However, without independent information regarding the $v4=1$ level, detailed analyses of the perturbations are not possible. $\mathrm{<mrow\; data-mjx-texclass="ORD">\ast </mrow>}$ Research carried out at Brookhaven National Laboratory was performed under contract DE-AC02-76CH00016 with the U. S. Department of Energy and supported by its Division of Chemical Sciences. $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ T. J. Sears, P. R. Bunker, P. B. Davies, S. A. Johnson and V. \u{S}pirko, J. Chem. Phys. 83, 2676 (1985).