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Formation of even-numbered hydrogen cluster cations in ultracold helium droplets.

Formation of even-numbered hydrogen cluster cations in ultracold helium droplets.

Authors :
Jaksch, S.
Mauracher, A.
Bacher, A.
Denifl, S.
Ferreira da Silva, F.
Schöbel, H.
Echt, O.
Märk, T. D.
Probst, M.
Bohme, D. K.
Scheier, P.
Source :
Journal of Chemical Physics; 12/14/2008, Vol. 129 Issue 22, p224306, 8p, 1 Diagram, 1 Chart, 5 Graphs
Publication Year :
2008

Abstract

Neutral hydrogen clusters are grown in ultracold helium nanodroplets by successive pickup of hydrogen molecules. Even-numbered hydrogen cluster cations are observed upon electron-impact ionization with and without attached helium atoms and in addition to the familiar odd-numbered H<subscript>n</subscript><superscript>+</superscript>. The helium matrix affects the fragmentation dynamics that usually lead to the formation of overwhelmingly odd-numbered H<subscript>n</subscript><superscript>+</superscript>. The use of high-resolution mass spectrometry allows the unambiguous identification of even-numbered H<subscript>n</subscript><superscript>+</superscript> up to n≅120 by their mass excess that distinguishes them from He<subscript>n</subscript><superscript>+</superscript>, mixed He<subscript>m</subscript>H<subscript>n</subscript><superscript>+</superscript>, and background ions. The large range in size of these hydrogen cluster ions is unprecedented, as is the accuracy of their definition. Apart from the previously observed magic number n=6, pronounced drops in the abundance of even-numbered cluster ions are seen at n=30 and 114, which suggest icosahedral shell closures at H<subscript>6</subscript><superscript>+</superscript>(H<subscript>2</subscript>)<subscript>12</subscript> and H<subscript>6</subscript><superscript>+</superscript>(H<subscript>2</subscript>)<subscript>54</subscript>. Possible isomers of H<subscript>6</subscript><superscript>+</superscript> are identified at the quadratic configuration interaction with inclusion of single and double excitations (QCISD)/aug-cc-pVTZ level of theory [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00219606
Volume :
129
Issue :
22
Database :
Complementary Index
Journal :
Journal of Chemical Physics
Publication Type :
Academic Journal
Accession number :
35763955
Full Text :
https://doi.org/10.1063/1.3035833