Hannover 2010 – scientific programme

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MO: Fachverband Molekülphysik

MO 6: Cold Molecules I

MO 6.4: Talk

Tuesday, March 9, 2010, 15:00–15:15, F 142

Absolute and near threshold photodetachment cross sections of negative ions — •Rico Otto¹, Petr Hlavenka¹, Thorsten Best¹, Sebastian Trippel¹, Martin Stei¹, Matthias Weidemüller², and Roland Wester¹ — ¹Physikalisches Institut, Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg — ²Physikalisches Institut, Universität Heidelberg, Albert-Überle-Str. 3-5, 69120 Heidelberg

The photodetachment of a weakly bound electron from an anion represents a fundamental light-matter interaction. We have developed a laser depletion tomography method that allows us to measure absolute photodetachment cross sections in a multipole radiofrequency trap with high accuracy. We use this method to study the O⁻ cross section, which shows a significant deviation from ab initio calculations. The total cross sections of molecular OH⁻ measured at 662 nm and 632 nm are found to be constant in the temperature range 8-300 K [1]. Near threshold photodetachment is sensitive for internal excitations of molecular ions. Here we also present first studies to use this as a sensitive tool for determining internal temperatures of trapped ions. In future experiments this will be used to study the temperature of bigger molecular systems like water clusters.
P. Hlavenka et al., J. Chem. Phys. 130, 061105 (2009)