Fe b 20 18 A Helium-Surface Interaction Potential of Bi 2 Te 3 ( 111 ) from Ultrahigh-Resolution Spin-Echo Measurements

We have determined an atom-surface interaction potential for the He–Bi2Te3(111) system by analysing ultrahigh resolution measurements of selective adsorption resonances. The experimental measurements were obtained using He spin-echo spectrometry. Following an initial free-particle model analysis, we use elastic close-coupling calculations to obtain a three-dimensional potential. The three-dimensional potential is then further refined based on the experimental data set, giving rise to an optimised potential which fully reproduces the experimental data. Based on this analysis, the He–Bi2Te3(111) interaction potential can be described by a corrugated Morse potential with a well depth D = (6.22 ± 0.05) meV, a stiffness κ = (0.92 ± 0.01) Å −1 and a surface electronic corrugation of (9.6 ± 0.2)% of the lattice constant. The improved uncertainties of the atom-surface interaction potential should also enable the use in inelastic closecoupled calculations in order to eventually study the temperature dependence and the line width of selective adsorption resonances.