Muon decay channelling and the Mu* site in silicon

An implanted radioactive impurity such as a positive muon in silicon will exhibit the steering or channelling effect of the host lattice on the trajectory of its charged decay particle. A measurement of the angular distribution of such decay particles along crystal directions close to high symmetry axes and planes will show maxima and minima due to the coherent small angle scattering. Such channelling features can be used to determine the site of the radioactive impurity in the host lattice. For positively charged decay particles, a maximum (minimum) in the angular distribution will occur for a site which is in a channel (host atom shadow) for a projection along the observation direction. The authors have performed such angular distribution measurements for 30 to 50 MeV decay positrons from positive muon decay. (Auth.)