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Oriented O(3P2), Ne(3P2), and He(3S1) atoms emerging from a bent magnetic guide
Authors:Justin Jankunas  Kevin S. Reisyan  T. Peter Rakitzis
Affiliation:1. Institute for Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland;2. Department of Physics, University of Crete, and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, Heraklion-Crete, Greece
Abstract:We describe our observation of strongly oriented total electronic angular momentum J in O(3P2), Ne(3P2), and He(3S1) atoms emerging from a bent magnetic multipole guide, as measured by resonant multiphoton ionisation. This was contrary to our expectation because no additional (uniform) magnetic fields were applied to orient the atoms behind the exit of the guide. Two- and three-photon ionisation techniques were employed to determine the degree of J polarisation, from which we infer that atoms become oriented as a result of a combination of weak fringe fields, possible stray fields, and the fact that molecular beam packets do not oscillate around the geometric center of the bent multipole guide. We conclude that similar effects may exist in other, related experiments and that a detailed characterisation of the degree of orientation is required prior to any study of chemical dynamics or spectroscopy. This paper should serve as a warning for anybody using similar devices not to assume isotropic angular momentum distributions of atoms and molecules emerging from a magnetic guide or a decelerator, particularly when it is bent; whenever possible, the possibility for a J anisotropy should be experimentally checked.
Keywords:Oriented atoms  atom guides  reaction dynamics  crossed beams  merged beams
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