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MO: Molekülphysik
MO 57: Poster: Cold Molecules
MO 57.1: Poster
Thursday, March 16, 2006, 16:30–18:30, Labsaal
Towards laser induced reactions of negative ions in a cold 22-pole ion trap — •S. Trippel, R. Berhane, R. Otto, J. Mikosch, M. Weidemüller, and R. Wester — Physikalisches Institut, Universität Freiburg, 79104 Freiburg
Radio-frequency traps are widely used to store and investigate ions. In the last decade it became clear, that collisional cooling of vibrations and rotations of molecular ions in a rf-trap requires high order multipole fields. Therefore we employ a 22-pole rf-ion trap to prepare molecular ions in certain rovibrational states and to investigate the influence of this preparation on chemical reactions such as OH− + H2 —→ H2O + H−. This reaction is predicted to be exoergic only if the OH− ion populates a vibrational level v≥2. Exciting one of these levels with laser light will induce a reaction and allows for a precise spectroscopy of the involved levels and a diagnostics of the rotational level population of OH− in the trap [1]. Currently a 10 K cooling system for the trap is constructed to cool OH− to a single rotational state. The status of the experiment and the next steps to measure rotational state-specific collision rates at low temperatures will be described. Simulations based on the Debye-Hückel model are presented which yield predictions for the radial distribution of the trapped ions. Furthermore, the design for a new micro-ion-trap, developed in cooperation with the Institute of Microfabrication at the University of Freiburg, is presented.
[1] J. Mikosch, H Kreckel, R. Wester, R. Plašil and J. Glosík, D. Gerlich, D. Schwalm and A. Wolf, J.Chem.Phys. 121, 11030 (2004)