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 Title: Terahertz measurements of hot hydronium ions (H3O+)with an extended negative glow discharge Author(s): Pearson, John Contributor(s): Yu, Shanshan Subject(s): Mini-symposium: Astronomical Molecular Spectroscopy in the Age of ALMA Abstract: Terahertz absorption spectroscopy was employed to detect the ground-state inversion transitions of the hydronium ion. The highly excited ions were created with an extended negative glow discharge through a gas mixture of 1 mtorr of H$_2$O, 2 mtorr of H$_2$, and 12 mtorr of Ar, which allowed observation of transitions with $J$ and $K$ up to 12. In total forty seven transitions were measured in the 0.9--2.0 THz region and twenty two of them were observed for the first time. The experimental uncertainties range from 100 to 300~kHz, which are much better than those of 0.3--1.2~MHz reported in previous work. Differences up to 25.6~MHz were found between the observed positions and the catalog values that have been used for Herschel data analysis of observations towards Sagittarius B2(N), NGC 4418 and Arp 220.\footnote{Lis et al., \lq\lq Hot, metastable hydronium ion in the Galactic center: formation pumping in X-ray-irradiated gas?\rq\rq, {\em Phil.\ Trans.\ R.\ Soc.\ A}~{\bf 370}, 5162 (2012).}\footnote{Gonz\'alez-Alfonso et al., \lq\lq Excited OH$^+$, H$_2$O$^+$ and H$_3$O$^+$ in NGC 4418 and Arp 220\rq\rq, {\em Astrophys.\ Astronom} {\bf 550}, A25 (2013).} The new and improved measurements were fit to experimental accuracies with an updated Hamiltonian; and better H$_3$O$^+$ predictions are reported to support the proper analysis of astronomical observations by high-resolution spectroscopy telescopes, such as Herschel,\footnote{Lis et al., \lq\lq Widespread rotaional-hot hydronium in the Galactic Interstellar Medium\rq\rq, {\em Astrophys.\ J.}, submitted (2014).} SOFIA, and ALMA. Issue Date: 2014-06-19 Publisher: International Symposium on Molecular Spectroscopy Citation Info: Pearson, J.; Yu, S. TERAHERTZ MEASUREMENTS OF HOT HYDRONIUM IONS (H3O+) WITH AN EXTENDED NEGATIVE GLOW DISCHARGE. Proceedings of the International Symposium on Molecular Spectroscopy, Urbana, IL, June 16-21, 2014. DOI: 10.15278/isms.2014.RA03 Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/51192 DOI: https://doi.org/10.15278/isms.2014.RA03 Rights Information: Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/ Date Available in IDEALS: 2014-09-172015-04-14
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