Issue 5, 2005
From the journal:

Physical Chemistry Chemical Physics

H6+ in irradiated solid para-hydrogen and its decay dynamics: Reinvestigation of quartet electron paramagnetic resonance lines assigned to H2−

Takayuki Kumada,*a   Hiroto Tachikawab  and  Toshiyuki Takayanagic  

* Corresponding authors

a Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki, Japan
E-mail: kumada@popsvr.tokai.jaeri.go.jp
Fax: +81 29 282 5927
Tel: +81 29 282 6031

b Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo, Japan
E-mail: hiroto@eng.hokudai.ac.jp
Fax: +81 11 706 7897
Tel: +81 11 706 6750

c Department of Chemistry, School of Science, Saitama University, Saitama, Japan
E-mail: tako@chem.saitama-u.ac.jp
Fax: +81 48 858 3700
Tel: +81 48 858 9113

Abstract

The quartet electron paramagnetic resonance (EPR) lines observed in γ- and X-ray irradiated solid para-H2, which have previously been assigned to H2−, are reinvestigated. We have reassigned the quartet lines to H6+ rather than H2− mainly due to comparison of experimentally obtained EPR parameters to theoretical results. Based on the new assignment, trapping site, rotation, ortho–para conversion, quantum diffusion and isotope effect of H6+ have been reinterpreted by the precise reanalysis as follows. The H6+ ion is composed of the collinearly aligned H2+ core at the center and two H2 rotors at both ends, occupies a single substitutional site, and has a precession motion around a crystalline axis with the angle of ∼57°. The ortho–para conversion of H2+ core of H6+ is completed within the time-scale of hours, whereas ortho-H2 molecules near H6+ convert much faster. H6+ diffuses quantum mechanically by the repetition of H6+ + H2 → H2 + H6+ reaction. The diffusion terminates by the reaction, H6+ + HD → H5D++ H2, with a HD impurity contained in the para-H2 sample at natural abundance. Finally, we will propose a possible reason why H6+ is produced instead of H3+ in the irradiated solid H2.

Graphical abstract: H6+ in irradiated solid para-hydrogen and its decay dynamics: Reinvestigation of quartet electron paramagnetic resonance lines assigned to H2−

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Article information

DOI
https://doi.org/10.1039/B415179H
Article type
Paper
Submitted
30 Sep 2004
Accepted
07 Jan 2005
First published
20 Jan 2005

Phys. Chem. Chem. Phys., 2005,7, 776-784

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H6+ in irradiated solid para-hydrogen and its decay dynamics: Reinvestigation of quartet electron paramagnetic resonance lines assigned to H2−

T. Kumada, H. Tachikawa and T. Takayanagi, Phys. Chem. Chem. Phys., 2005, 7, 776 DOI: 10.1039/B415179H

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