Experimental evidence for the existence of an electronically excited state of the proposed dihydrogen radical cation He-H-H-He
In a recent report, Uggerud and co-workers (A. Krapp et al., Chem. Eur. J. 2008. 14, 4028) proposed the existence of, a flew class of, radical cations in which a dihydrogen bridges two identical main group elements. Upon electron impact ionization of helium nanodroplets doped with one or more H(2) molecules we observe various He(x)H(y)(+) cluster ions, including He(2)H(2)(+), which would belong to the proposed class of radical cations. Mass-analyzed kinetic energy scans reveal that the ion is metastable; it dissociates in the field-free region of the mass spectrometer. One reaction is into HeH(2)(+) + He with a low kinetic energy release of 15 4 meV. Surprisingly, another unimolecular reaction is Observed. into HeH(+) + HeH (or He + H). The probability of this reaction is ail order of magnitude higher, and the average kinetic energy release is four times larger. These findings suggest the presence of a metastable electronically excited stated they arc consistent with the proposed linear, centrosymmetric ion structure of He-H-H-He(+).
Chemistry-a European Journal
WILEY-V C H VERLAG GMBH
Digital Object Identifier (DOI)
Jaksch, Stefan; da Silva, Filipe Ferreria; Denifl, Stephan; Echt, Olof E.; Maerk, Tilmann D.; and Scheier, Paul, "Experimental evidence for the existence of an electronically excited state of the proposed dihydrogen radical cation He-H-H-He " (2009). Chemistry-a European Journal. 41.
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