PENDELLOSUNG OSCILLATIONS IN 2ND-ORDER BRAGG SCATTERING OF ATOMS FROMA STANDING LIGHT-WAVE

Bragg scattering of atoms from a standing light wave exhibits Pendello sung oscillations in the scattering probability. For second-order scat tering, we have recently observed significant deviation of the oscilla tion frequency from the prediction for a pure four-photon-type process . To give a quantitative explanation for this behaviour, we present an analytical calculation which takes into account lowest energy momentu m states. Our calculation suggests that a transition between a four-ph oton-type process at low light intensity to a two-photon-type process at higher light intensity is responsible for this behaviour.