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MO: Fachverband Molekülphysik

MO 9: Kalte Moleküle II (gemeinsam mit Q)

MO 9.7: Talk

Tuesday, March 11, 2008, 12:30–12:45, 3G

Photodetachment of cold negative ions — •Petr Hlavenka, Rico Otto, Sebastian Trippel, Jochen Mikosch, Mathias Weidemüller, and Roland Wester — Physikalisches Institut, Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg

With the recent detection of negative carbon clusters in the interstellar molecular clouds, laboratory studies of negative ions are becoming exceedingly important. We study absolute OH⁻ photodetachment cross sections as a model for the low temperature behavior of this fundamental light-matter interaction, which is a main loss channel of the anions in interstellar medium (ISM). To reach ISM-relevant conditions we study the photodetachment interaction of laser light with anions captured in a 22-pole RF trap [1]. The sympathetic cooling of ions captured in the flat effective potential yields well defined rotational-state distributions. We record the relative loss of stored anions due to the photodetachment while scanning the volume of the trap with a focussed, 2D movable laser beam. A column-density map and the absolute photodetachment cross section are obtained. We present results for OH⁻ photodetachment at different temperatures and laser wavelengths. This gives insight to the rotational dependence of the photodetachment process,which gives us better understanding of the processes leading to the anion abundances in the ISM.

[1] S. Trippel et al., Phys. Rev. Lett. 97, 193003 (2006)