Time-of-flight scattering and recoiling spectrometry. III. The structure of hydrogen on the W(211) surface

The technique of time-of-flight scattering and recoiling spectrometry (TOF-SARS) with detection of both neutrals and ions is applied to structural analysis of hydrogen adsorbed at saturation coverage on a W(211) surface in the temperature range 100 °C to 200 °C. Scattering and recoiling spectra, induced by pulsed ${\mathrm{Ne}}^{+}$ and ${\mathrm{Ar}}^{+}$ primary-ion beams, are monitored as a function of polar beam incident angle α, surface azimuthal angle δ, scattering angle θ, recoiling angle φ, and ejection angle β. Plots of hydrogen recoil intensities in (α,δ) space provide recoiling structural contour maps and recoiling structural plots which are representative of the recoil symmetry of hydrogen on the W(211) surface. Measurements of recoil (both direct and surface recoils) intensities as a function of α and β along different azimuths δ provide experimental values of the critical incident angle ${\alpha }_c$,sh for shadowing and the critical ejection angle ${\beta }_c$ (or ${\alpha }_c$,bl) for blocking by neighboring atoms.