Rotationally induced Penning ionization of ultracold photoassociated helium dimers

Abstract

We have studied photoassociation of metastable \tripS helium atoms near the \tripS-\tripP asymptote by both ion detection in a magneto-optical trap and trap-loss measurements in a magnetic trap. A detailed comparison between the results of the two experiments gives insight into the mechanism of the Penning ionization process. We have identified four series of resonances corresponding to vibrational molecular levels belonging to different rotational states in two potentials. The corresponding spin states become quasi-purely quintet at small interatomic distance, and Penning ionization is inhibited by spin conservation rules. Only a weak rotational coupling is responsible for the contamination by singlet spin states leading to a detectable ion signal. However, for one of these series Bose statistics does not enable the rotational coupling and the series detected through trap-loss does not give rise to sufficient ionization for detection.

arXiv comment7 pages, 4 figures, submitted to EuroPhysics Letters

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Cited by in corpus (4)

• Formation and interactions of cold and ultracold molecules: new challenges for interdisciplinary physics
• Long-range interactions between a He($2^{3}S$) atom and a He($2^{3}P$) atom for like isotopes
• Effects of non-adiabatic and Coriolis couplings on the bound states of He(2 ^3S)+He(2 ^3P)
• On the Role of Penning Ionization in Photoassociation Spectroscopy