Erlangen 2022 – scientific programme

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MO: Fachverband Molekülphysik

MO 7: Cold Molecules

MO 7.1: Talk

Tuesday, March 15, 2022, 10:30–10:45, MO-H8

Spin-state-controlled Penning collisions between metastable helium atoms and ground-state lithium atoms — •Tobias Sixt, Frank Stienkemeier, and Katrin Dulitz — Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg im Breisgau, Germany

In our experiment, we study quantum-state-controlled Penning collisions between metastable helium atoms (He*) and ultracold lithium atoms (Li) in order to investigate efficient ways of controlling the outcome of such ionizing collisions. For this, we have combined a supersonic-beam source for He* with a magneto-optical trap (MOT) for Li. In order to distinguish in between the contributions of He(2³S₁) and He(2¹S₀) to the reaction rate, we deplete the population of He* atoms in the 2¹S₀ level using a novel optical-excitation scheme. Furthermore, we use laser-optical pumping to prepare both He(2³S₁) and Li(2²S_1/2) in selected magnetic sub-levels prior to the collision.

In this contribution, we demonstrate the efficient control of He(2³S₁)-Li(2²S_1/2) Penning ionization by spin-state preparation. Our results imply a strong suppression (enhancement) of Penning-ionizing collisions for non-spin-conserving (spin-conserving) reaction channels. Our results are in good agreement with a model based on spin angular momentum coupling of the prepared atomic states to the molecular reaction channels. Small deviations from the model indicate the contribution of quartet states to the reaction rate, which is in violation of spin-conservation rules.