ESR study of H6+ and H4D2+ produced in irradiated solid hydrogens

We reinvestigated the quartet ESR lines with g-value g≈2.002 and hyperfine coupling constant A≈20 mT produced in γ-ray irradiated solid p-H2 in order to determine to which the lines should be assigned, H2− or H6+. We newly found further splitting of each of the quartet lines into quintet ones in irradiated solid p-H2 containing o-D2 at 1 mol%. ESR parameters of these new lines were found to be consistent with those of H4D2+ calculated. This result supports the assignment to H6+ rather than H2−.