Diffraction of ultracold neutrons on a moving grating and neutron focusing in time

We report the results of two experiments on non-stationary neutron optics. In the first one we measured the spectrum of ultracold neutrons (UCN) diffracted on a phase grating moving across the beam. A discrete spectrum is found in good agreement with theory. This purely quantum effect may be interpreted as resulting from phase modulation of the neutron wave. In the second experiment we observed the UCN focusing in time. Periodical acceleration and deceleration of neutrons is produced by diffraction on a phase grating with a variable space period.