2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/120985We report the slowing of a supersonic beam by elastic reflection from a receding atomic mirror. We use a pulsed supersonic nozzle to generate a 511 +/- 9 m/s beam of helium that we slow by reflection from a Si(111)-H(1x1) crystal placed on the tip of a spinning rotor. We were able to reduce the velocity of helium by 246 m/s and show that the temperature of the slowed beam is lower than 250 mK in the co-moving frame.Atomic Physicstext