Investigations of “soft-landed” Cd surface atoms via nuclear methods: hyperfine-field sign determination

Using refined preparation techniques, cadmium guest atoms have been positioned at different sites on the surfaces of nickel crystals. The magnetic hyperfine fields and the electric field gradients at the Cd nuclei were measured by time-dependent perturbed angular correlation (TDPAC) spectroscopy of the emitted gamma radiations. By measuring the combined interactions, electric field gradients and magnetic hyperfine fields can be unambiguously attributed to each surface site. The signs of the magnetic hyperfine fields are determined by applying an external magnetic field and choosing the appropriate γ-ray detector configuration. The measured fields correlate with the number of neighbouring host atoms. Band structure calculations confirm this finding and predict magnetic fields for various sp elements from the band structure of the s-like conduction electrons. The quadrupolar interactions are manifestations of the balance in the occupation of the guest p-sublevels. These results provide new information on the structure and formation of electronic configurations of sp elements in different local environments and will contribute to understanding electronic effects on surfaces.