Diffusion of slow positrons from gold

An attempt has been made to experimentally determine the diffusion length L D of slow positrons (peak energy ~0.1 eV) in gold at room temperature by comparing the slow positron yield with phenomenological models for the yield. The diffusion of the slow positron is assumed to be similar to that of a thermal neutron diffusion in an absorbing and scattering medium. A collision mean free path of the slow positron in the electron gas under the Born approximation is estimated to be ~2 Å. This corresponds to a calculated value of the diffusion length L D ~250 Å. The experimental value is [Formula: see text].