# Zeeman Relaxation of Cold Atomic Iron and Nickel in Collisions with $$^3$$He

 Title: Zeeman Relaxation of Cold Atomic Iron and Nickel in Collisions with $$^3$$He Author: Johnson, Cort; Newman, Bonna; Brahms, Nathan; Doyle, John M.; Kleppner, Daniel; Greytak, Thomas J. Note: Order does not necessarily reflect citation order of authors. Citation: Johnson, Cort, Bonna Newman, Nathan Brahms, John M. Doyle, Daniel Kleppner, and Thomas J. Greytak. 2010. Zeeman relaxation of cold atomic iron and nickel in collisions with $$^3$$He. Physical Review A 81(6): 062706. Full Text & Related Files: 1003.1106v1.pdf (554.8Kb; PDF) Abstract: We have measured the ratio γ of the diffusion cross section to the angular momentum reorientation cross section in the colliding Fe-$$^3$$He and Ni-$$^3$$He systems. Nickel (Ni) and iron (Fe) atoms are introduced via laser ablation into a cryogenically cooled experimental cell containing cold (<1 K) $$^3$$He buffer gas. Elastic collisions rapidly cool the translational temperature of the ablated atoms to the $$^3$$He temperature. γ is extracted by measuring the decays of the atomic Zeeman sublevels. For our experimental conditions, thermal energy is comparable to the Zeeman splitting. As a result, thermal excitations between Zeeman sublevels significantly impact the observed decay. To determine γ accurately, we introduce a model of Zeeman state dynamics that includes thermal excitations. We find γ$$_{Ni-^{3}He}=5×10^3$$ and γ$$_{Fe-^{3}He}\leq3×10^3$$ at 0.75 K in a 0.8 T magnetic field. These measurements are interpreted in the context of submerged shell suppression of spin relaxation, as studied previously in transition metals and rare earth atoms. Published Version: doi:10.1103/PhysRevA.81.062706 Other Sources: dspace.mit.edu/openaccess-disseminate/1721.1/60905 Terms of Use: This article is made available under the terms and conditions applicable to Open Access Policy Articles, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#OAP Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:8866870