Reflection of atoms from a pulsed evanescent wave

Department of Engineering Physics and Mathematics, Helsinki University of Technology - FIN-02150 Espoo, Finland

Received: 15 April 1996
Accepted: 2 October 1996

Abstract

Atomic motion in a pulsed evanescent wave, with a pulse duration on the order of the lifetime of the excited state, is calculated using the semiclassical Bloch-equation approach. The equations for the internal atomic motion are solved using two approximations based on high laser intensity and on slow atomic velocity. The center-of-mass motion in the field under the effect of the dipole force is subsequently determined by numerical integration. As an example, the calculations show that the maximum normally incident velocity allowing a sodium atom to be reflected is approximately 35 m/s when using a laser pulse of 7 ns duration. Our results also demonstrate that the velocity distribution of the reflected atoms may considerably differ from the distribution of the incident atoms due to different deceleration and acceleration times in a short laser pulse. This effect may lead to an average slowing-down of the reflected part of a thermal particle beam.