SAMOP 2021 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 9: Poster 2
MO 9.2: Poster
Freitag, 24. September 2021, 17:30–19:30, P
New Lifetime Limit of the Ground State Vinylidene Anion H2CC− — •Felix Nuesslein1, Klaus Blaum1, Jürgen Göck1, Manfred Grieser1, Sebastian George2, Robert von Hahn1, Ábel Kálosi3,1, Holger Kreckel1, Damian Müll1, Oldřich Novotný1, Henrik Pedersen4, Viviane Schmidt1, and Andreas Wolf1 — 1Max-Planck-Institut für Kernphysik, Heidelberg, 69117, Germany — 2Institut für Physik, Universität Greifswald, Greifswald, 17487, Germany — 3Columbia Astrophysics Laboratory, Columbia University, New York, 10027, USA — 4Department of Physics and Astronomy, Aarhus University, Aarhus, 8000, Denmark
The isomers acetylene (HCCH) and vinylidene (H2CC) form one of the simplest systems for studying isomeric reactions involving hydrogen. In anionic form the vinylidene isomer has the lowest total energy with an electron affinity of ∼0.5 eV. It lies 1.5 eV above the lowest neutral level of acetylene, which gives rise to the hypothesis that isomerization linked with electron emission could limit the lifetime of H2CC−. An experiment at a room-temperature storage ring obtained a finite lifetime of ∼110 s [1] by extrapolating from collision-limited (∼ 10 s) to collision-free beam lifetimes of H2CC− and a stable reference ion. To access longer ion beam lifetimes (up to 3000 s) and thereby enable a better estimate of the ground state H2CC− lifetime, we employed the Heidelberg electrostatic Cryogenic Storage Ring [2]. From comparing the decays of H2CC− and the stable reference ion CN− we find that the ground state H2CC− lives at least 3500 s, i.e., more than an order of magnitude longer than assumed previously. The latest results will be presented.
[1] M. Jensen et al., Phys. Rev. Lett. 84 (2000) 1128.
[2] R. von Hahn et al., Rev. Sci. Instrum. 87 (2016) 063115.