Binary and ternary recombination of para-${\rm H}_3^+$H3+ and ortho-${\rm H}_3^+$H3+ with electrons: State selective study at 77–200 K

Measurements in \documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ afterglow plasmas with spectroscopically determined relative abundances of \documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ ions in the para-nuclear and ortho-nuclear spin states pr...

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Veröffentlicht in:The Journal of chemical physics 2012-06, Vol.136 (24)
Hauptverfasser: Dohnal, Petr, Hejduk, Michal, Varju, Jozef, Rubovič, Peter, Roučka, Štěpán, Kotrík, Tomáš, Plašil, Radek, Glosík, Juraj, Johnsen, Rainer
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Sprache:eng
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Zusammenfassung:Measurements in \documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ afterglow plasmas with spectroscopically determined relative abundances of \documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ ions in the para-nuclear and ortho-nuclear spin states provide clear evidence that at low temperatures (77–200 K) para-\documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ ions recombine significantly faster with electrons than ions in the ortho state, in agreement with a recent theoretical prediction. The cavity ring-down absorption spectroscopy used here provides an in situ determination of the para/ortho abundance ratio and yields additional information on the translational and rotational temperatures of the recombining ions. The results show that \documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ recombination with electrons occurs by both binary recombination and third-body (helium) assisted recombination, and that both the two-body and three-body rate coefficients depend on the nuclear spin states. Electron-stabilized (collisional-radiative) recombination appears to make only a small contribution.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4730162