Reflection of atoms from a pulsed evanescent wave

Author： Ryytty P. Kaivola M. Aminoff C. G.

E-ISSN： 1286-4854|36|5|343-348

ISSN： 0295-5075

Source： EPL (EUROPHYSICS LETTERS), Vol.36, Iss.5, 2010-03, pp. : 343-348

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Abstract

Atomic motion in a pulsed evanescent wave, with a pulse duration onthe order of the lifetime of the excited state, is calculated usingthe semiclassical Bloch-equation approach. The equations for theinternal atomic motion are solved using two approximations based onhigh laser intensity and on slow atomic velocity. The center-of-massmotion in the field under the effect of the dipole force issubsequently determined by numerical integration. As an example, thecalculations show that the maximum normally incident velocity allowinga sodium atom to be reflected is approximately 35 m/s when using a$\rm 10\;MW/cm^2$ laser pulse of 7 ns duration. Our results alsodemonstrate that the velocity distribution of the reflected atoms mayconsiderably differ from the distribution of the incident atoms due todifferent deceleration and acceleration times in a short laserpulse. This effect may lead to an average slowing-down of thereflected part of a thermal particle beam.