Requirements for coherent atom channeling

The evolution of atomic de Broglie waves inside strong periodic potentials can be described as channeling and exhibits both particle and wave effects. Using a beam of metastable Argon atoms interacting with an intense standin g light. wave we detect an interference pattern arising from the coherent g uiding of the atoms through the light channels. In analogy to light optics these interference effects art: only visible, if certain requirements for l ongitudinal and transverse coherence are fulfilled. We experimentally study the influence of the velocity selection and the collimation of the Argon a toms. As well as an another factor determining the coherence of the evoluti on - the spontaneous emission. (C) 2000 Elsevier Science B.V. All rights re served.