Hannover 2013 – scientific programme

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MO: Fachverband Molekülphysik

MO 29: Collisions and Energy Transfer

MO 29.1: Talk

Friday, March 22, 2013, 11:00–11:15, F 107

Vibrational autodetachment of sulfur hexafluoride anions — Sebastian Menk¹, Klaus Blaum¹, Swarup Das², Michael Froese¹, •Michael Lange¹, Manas Mukherjee², Roland Repnow¹, Robert von Hahn¹, Dirk Schwalm^1,3, and Andreas Wolf¹ — ¹Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg — ²Raman Center for Atomic Molecular and Optical Sciences, Kolkata 700 032, India — ³Weizmann Institute of Science, Rehovot, 76100, Israel

We have measured the rate of electron emission from vibrationally highly excited SF₆⁻ ions in a cryogenic ion beam trap. By following the emission rate over five orders of magnitudes and for up to 100 ms, we have found a deviation from the expected power function. While this is in part due to radiative cooling, we have observed the power function and the deviation from it to depend on the excitation conditions in the ion source, indicating the influence of the detachment of near-threshold states. We have therefore for the first time applied a statistical rate model that takes into account the microscopic detail of the emission mechanism and the ro-vibrational structure of the anion and the neutral molecule. Our results support the adiabatic electron affinity and the very low emission rate from states just over the threshold that have been predicted in recent theoretical investigations, with deviations being compatible with the expected effects of the rotational and vibrational temperatures of the ions and uncertainties of the model itself. We also present results from an experiment where the ions were re-excited with a laser after the initial decay had subsided.