Neutron holography and diffuse scattering of palladium hydride

To extract a pure atomic-resolution hologram around hydrogen from a two-dimensional (2D) neutron intensity distribution around a single crystal, enhancement of the holographic signal and suppression of the diffuse scattering are important; sample cooling can achieve both. To estimate the performance of sample cooling in achieving these requirements, the angular anisotropy of the neutron intensities around a PdH0.78 single crystal was measured at 300 K and 100 K. In addition to the reduction in the diffuse scattering intensity, the pattern itself changed markedly upon sample cooling, thus indicating a significant modification of the hydrogen lattice dynamics. The reconstruction from a hologram, which was obtained by subtracting the diffuse scattering pattern, shows images of H and Pd nuclei as negative and positive peaks, respectively. In particular, such reconstruction at 100 K exhibits distinct H images at distant positions owing to the suppression of hydrogen motion. These features are important for the determination of hydrogen sites in various materials.