Terahertz Measurements of Hot Hydronium Ions (h3o+) With an Extended Negative Glow Discharge
Year: 2014
Type: conference-paper
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.
Authors: John Pearson, Shanshan Yu
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2023461060