Low velocity quantum reflection of Bose-Einstein condensates
  We studied quantum reflection of Bose-Einstein condensates at normal incidence on a square array of silicon pillars. For incident velocities of 2.5-26 mm/s observations agreed with theoretical predictions that the Casimir-Polder potential of a reduced density surface would reflect slow atoms with much higher probability. At low velocities (0.5-2.5 mm/s), we observed that the reflection probability saturated around 60% rather than increasing towards unity. We present a simple model which explains this reduced reflectivity as resulting from the combined effects of the Casimir-Polder plus mean field potential and predicts the observed saturation. Furthermore, at low incident velocities, the reflected condensates show collective excitations. 
T. A. Pasquini, M. Saba, G. Jo, Y. Shin, W. Ketterle, D. E. Pritchard,   T. A. Savas, N. Mulders