Soft-landing deposition of radioactive probe atoms on surfaces

We present a method to deposit a wide range of radioactive probe atoms on surfaces, without introducing lattice damage or contaminating the surface with other elements or isotopes. In this method, the probe atoms are mass-separated using an isotope separator, decelerated to 5 eV, and directly deposited on the surface. The method allows for performing hyperfine interactions experiments using trace amounts of radioactive probes located at surfaces and interfaces. The characteristics of the deposition method will be described, with particular attention to the deceleration stage of the isotope separator. The method was tested with perturbed angular correlation (PAC) experiments on the system In on Cu(17,1,1). The results are in agreement with molecular dynamics simulations of the deposition process. New developments, in particular the study of the self-diffusion of Ag atoms on Ag(100) by means of PAC with the 111Ag probe, are briefly discussed