ACCURATE MEASUREMENTS OF THE $J = 1 - 0$ TRANSITIONS OF H$_2$D$^+$ AND HD$_2^+$ USING LASER-INDUCED REACTIONS AND DETERMINATION OF SPECTROSCOPIC PARAMETERS FOR H$_2$D$^+$
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Date
2008
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The method of laser-induced reaction} {\bf 127} (2007) Art. No. 154317.} has been used for the first time to detect rotational transitions. The astronomically important $1_{01} - 0_{00}$ and $1_{11} - 0_{00}$ transitions of H$_2$D$^+$ and HD$_2^+$, respectively, have been recorded by observing the enhancement of their D/H isotope exchange reactions with $p$-H$_2$ upon rotational excitation in a cryogenic multipole ion trap. While the frequency for HD$_2^+$ is in good agreement with a previous, unpublished result,} {\bf 233} (2005) 7.} but more accurate, the frequency for H$_2$D$^+$ is some 60\,MHz lower than the value from the same unpublished source ($b$). The present H$_2$D$^+$ frequency has been fit together with previously published pure rotational transitions and with infrared ground state combination differences (GSCDs).} {\bf 364} (2006) 2943.} Starting values for spectroscopic parameters were derived from energies up to $J = K_a = 7$ calculated ab initio} {\bf 157} (1993) 237; J. Ramanlal and J. Tennyson, {\it Mon. Not. R. Astron. Soc.} {\bf 354} (2004) 161.} because of the smallness of the data set. Since the molecular ion is fairly floppy, the Hamiltonian has been expanded in Euler functions} {\bf 233} (2005) 174.} up to 6th order. Omitting one GSCD because of a large residual, the remaining GSCDs were reproduced to almost 0.002\,cm$^{-1}$ releasing only 7 parameters. Thus, for the first time this IR spectroscopic data has been reproduced within experimental uncertainties. The pure rotational transitions were fit overall within the reported experimental uncertainties. In Ref.~$c$ the wrong $1_{01} - 0_{00}$ transition frequency required 11 parameters to fit the pure rotational transitions within experimental uncertainties, albeit with somewhat larger residuals for the GSCDs than in the present work.
Description
E.,g. O. Asvany et al., J. Chem. Phys.D. A. Jennings et al.; cited in T. Amano and T. Hirao, J. Mol. Spectrosc.Summarized in T. Amano, Phil. Trans. R. Soc. AO. L. Polyansky et al., J. Mol. Spectrosc.H. M. Pickett et al., J. Mol. Spectrosc.
Author Institution: I. Physikalisches Institut, Universitat zu Koln, 50937 Koln, Germany
Author Institution: I. Physikalisches Institut, Universitat zu Koln, 50937 Koln, Germany