INTERFEROMETRY WITH LASER-MANIPULATED COLD ATOMS

An atomic beam of laser-decelerated metastable neon atoms has been use d for the first experimental observation of an atomic beam diffracted by coherent transfer of two photon momenta from an evanescent standing laser field. The incident atomic beam of the laser-slowed neon atoms had a mean velocity of 25 m/s as it was transversely compressed to a d iameter below 0.15 mm and to sub-Doppler temperatures. Direct images o f diffraction patterns taken by a high-resolution two-dimensional dete ctor showed specular reflection of the beam of metastable neon atoms u p to 74 mrad and clearly the second diffraction order from 81 to 92 mr ad. Based on a new detection scheme, optical Ramsey fringes on the Mg intercombination line (lambda = 457 nm) have been demonstrated with a resolution of 4 kHz and an accuracy of 2 x 10(-15) using laser-cooled and trapped atoms. Applying a pulsed excitation scheme to the trapped ensemble, the Ramsey signals are nearly undisturbed by the relativisti c Doppler effect and phase errors of the Ramsey zones. The detection i s based on quantum amplification due to the electron shelving effect i n cooperation with the trap dynamics, monitored as decrease of the tra p fluorescence induced by the fast trapping transition. Simultaneously recorded Ramsey interferences on a thermal atomic beam allowed a dire ct measurement of the second-order Doppler shift. The relevance of the experiment to future frequency standards achieving a stability and an accuracy of better than 10(-15) are discussed. In an additional exper iment, the trap for the neutral Mg atoms was improved in such a way th at a picture of the fluorescence light of a single atom stored in the trap could be recorded.