R-matrix propagation study of He scattering from NaCl(001) and its Kr overlayer

For the first time, we employ the R-matrix propagation technique of Stechel et al. to model the diffraction of atomic helium from a bare NaCl(001) surface and also from a NaCl(001) surface with a Kr overlayer. The Kr/NaCl(001) has recently been reported by De Kieviet et al. as the only known commensurate overlayer system with square symmetry. To verify this theoretically, we solve the close-coupling equation. The R-matrix propagation technique is used, since it has many computational advantages and will be shown to yield efficient and accurate results for such systems. Once the final R-matrix is obtained from this propagation method, scattering information is extracted from the S-matrix. We obtain excellent agreement between calculated relative intensities derived from the S-matrix elements and experimental relative intensities for the He/NaCl(001) system, and good agreement for the more interesting and complex He–Kr/NaCl(001) system. Corrections for inelastic effects have been attempted using the Debye–Waller factor, resulting in little or no improvement.