# Inelastic Collisions of Atomic Antimony, Aluminum, Erbium and Thulium below 1 K

 Title: Inelastic Collisions of Atomic Antimony, Aluminum, Erbium and Thulium below 1 K Author: Connolly, Colin Bryant Full Text & Related Files: Connolly_gsas.harvard_0084L_10517.pdf (4.771Mb; PDF) Abstract: Inelastic collision processes driven by anistropic interactions are investigated below 1 K. Three distinct experiments are presented. First, for the atomic species antimony (Sb), rapid relaxation is observed in collisions with $$^4He$$. We identify the relatively large spin-orbit coupling as the primary mechanism which distorts the electrostatic potential to introduce significant anisotropy to the ground $$^4S_{3/2}$$ state. The collisions are too rapid for the experiment to fix a specific value, but an upper bound is determined, with the elastic-to-inelastic collision ratio $$\gamma \leq 9.1 x 10^2$$. In the second experiment, inelastic $$\mathcal{m}_J$$-changing and $$J$$-changing transition rates of aluminum (Al) are measured for collisions with $$^3He$$. The experiment employs a clean method using a single pump/probe laser to measure the steady-state magnetic sublevel population resulting from the competition of optical pumping and inelastic collisions. The collision ratio $$\gamma$$ is measured for both $$\mathcal{m}_J$$- and $$J$$-changing processes as a function of magnetic field and found to be in agreement with the theoretically calculated dependence, giving support to the theory of suppressed Zeeman relaxation in spherical $$^2P_{1/2}$$ states [1]. In the third experiment, very rapid atom-atom relaxation is observed for the trapped lanthanide rare-earth atoms erbium (Er) and thulium (Tm). Both are nominally nonspherical $$(L \neq 0)$$ atoms that were previously observed to have strongly suppressed electronic interaction anisotropy in collisions with helium $$(\gamma > 10^4-10^5, [2,3])$$. No suppression is observed in collisions between these atoms $$(\gamma \lesssim 10)$$, which likely implies that evaporative cooling them in a magnetic trap will be impossible. Taken together, these studies reveal more of the role of electrostatic anisotropy in cold atomic collisions. Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:9909637
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