Frankfurt 2006 – wissenschaftliches Programm
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MS: Massenspektrometrie
MS 2: Beschleuniger-Massenspektrometrie 2
MS 2.4: Vortrag
Montag, 13. März 2006, 17:15–17:30, H1
Discovery of Long-Lived Molecular Hydrogen Anions H2− and D2− — •Robin Golser1, Hubert Gnaser2, Walter Kutschera1, Alfred Priller1, Peter Steier1, and Anton Wallner1 — 1VERA Laboratorium, Institut für Isotopenforschung und Kernphysik, Universität Wien, Austria — 2Department of Physics, Universität Kaiserslautern, Germany
The negative hydrogen molecule H2− is the most fundamental molecular anion. Up to now it was considered short lived (of the order of 10−15s). Despite the very short lifetime, the H2− anion is believed to be of crucial importance in various hydrogen reactions. It also may have been important for the creation of molecular hydrogen H2 in the early stages of the Universe.
By sputtering a TiH2, or a TiD2 target with Cs+ ions we were able to clearly proof the “unexpected” existence of long-lived (of the order of 10−6s) hydrogen anions H2− and D2−. These anions were identified unambiguously by accelerator mass spectrometry (AMS) and later also by secondary-ion mass spectrometry (SIMS). SIMS gives minimum abundance ratios: H2−/H− = 3.5×10−6, D2−/D− = 3.0×10−5. From their flight times through the system, minimum lifetimes of the order of 10−6s can be inferred. This is in accordance with theoretical calculations that predict highly rotationally excited hydrogen anions to have lifetimes in the µs range [1]. A detailed study utilizing an electrostatic ion beam trap at the Weizmann Institute is in progress.
[1] R. Golser, H. Gnaser, W. Kutschera, A. Priller, P. Steier, A. Wallner, M. Cizek, J. Horacek, W. Domcke, Phys. Rev. Lett. 94, 223003 (2005).