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Goyette, Ian C.

Physics

2012

MS

The scattering of ultracold atoms from surfaces has been studied since the early days of quantum theory. This topic has only gained in importance as gases in the nanokelvin range have become experimentally accessible and manipulation of these ultracold atoms is explored as a means toward quantum information processing. An important quantity to consider in these systems is s(E), the probability that a particle will stick to a surface as a function of its incident energy. A threshold law for sticking describes how s(E) scales with energy as E -- 0. There are two established threshold laws, one which applies to neutral particles (s(E) ~ [radical symbol] E) and one for charged particles (s(E) ~ s₀ where 0 We find that for neutral particles, the threshold law is altered and tunable with temperature when the surface is out of thermal equilibrium with its surrounding environment. When the surface temperature exceeds that of the environment but is below a critical temperature the new threshold law becomes s(E) ~ E [Greek gamma], where (0 [less than or equal to] [Greek gamma] [less than or equal to] 1/2). Just above the critical temperature the threshold behavior becomes oscillatory while well above the critical temperature the threshold law for charged particles is recovered. Numerical results supporting the new threshold law are presented and the possibility of experimental observation discussed.