Surface science using molecular beam spin echo

We have developed a new experimental method for measuring extremely small changes in kinetic energy in a Bur of atoms or molecules. Here, we manipulate the magnetic moments of the species so as to create an echo signal. Using the nuclear spins in an atomic beam of He-3 we have demonstrated the power of this method. by resolving a change in energy of several neV. Due to the exclusive surface sensitivity and complete inertness of He atoms as a probe, He-3 spin echo (He-3-SE) seems an ideal method for studying slow motion in and on surfaces (e.g. diffusion). Therefore, we have added UHV surface science capabilities to the He-3-SE setup. We present the first results obtained with the completed apparatus and show that He-3-SE may give information on the dynamics at the surface on length scales up to tens of mu m.