We report an experiment demonstrating diffraction of cold neutrons by surface acoustic waves. We show that, in contrast to analogous experiments with light, the motion of the surface–acoustic-wave deformation of the surface requires significant modification of the diffraction equation applicable to stationary gratings. Diffracted beam intensities are in reasonable agreement with a simple theoretical treatment.

• Received 3 March 1987

DOI:https://doi.org/10.1103/PhysRevLett.58.2770