open access

https://hdl.handle.net/2115/87469

Measurements of Ortho-to-para Nuclear Spin Conversion of H-2 on Low-temperature Carbonaceous Grain Analogs : Diamond-like Carbon and Graphite

英語

2021-12-13

IOP Publishing

Astrophysical journal

923(1)

71

Hydrogen molecules have two nuclear spin isomers: ortho-H-2 and para-H-2. The ortho-to-para ratio (OPR) is known to affect chemical evolution as well as gas dynamics in space. Therefore, understanding the mechanism of OPR variation in astrophysical environments is important. In this work, the nuclear spin conversion (NSC) processes of H-2 molecules on diamond-like carbon and graphite surfaces are investigated experimentally by employing temperature-programmed desorption and resonance-enhanced multiphoton ionization methods. For the diamond-like carbon surface, the NSC time constants were determined at temperatures of 10-18 K and from 3900 +/- 800 s at 10 K to 750 +/- 40 s at 18 K. Similar NSC time constants and temperature dependence were observed for a graphite surface, indicating that bonding motifs (sp(3) or sp(2) hybridization) have little effect on the NSC rates.

学術雑誌論文

Accepted Manuscript

Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International

This is the Accepted Manuscript version of an article accepted for publication in Astrophysical journal. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://doi.org/10.3847/1538-4357/ac2a33.

0004-637X