Investigation of electron lifetimes in molybdenum with dilute substitutional impurities

We have measured the electronic lifetimes of the systems Mo(W), Mo(Ru), Mo(Fe) and Mo(U). The concentrations were ≈ 370PPM, 70PPM, 20PPM, and 50PPM respectively. For the first three systems, only the hole octahedron centered atH was investigated thoroughly for all angles and the data inverted to get point lifetimes. For Mo(U) the investigation was done over the entire Fermi surface with the aid of an on-line PDP 11/20 mini-computer. Only selective points were used on other pieces of the Fermi surface in order to avoid problems with degenerate frequencies. A careful determination of the effective masses was also made at all angles under investigation. The masses were found to be in disagreement with those of Leaver and Meyers (these masses were used in our orginal investigation) by as much as 20% in some orientations. The electronic lifetimes were nearly isotropic on the hole octahedron in all the alloy systems investigated. In Mo(U) the isotropy was found to extend to all thed-like surfaces. Only thes-p-like hole ellipsoids centered atN possibly have a substantially different lifetime, but its measurement is inaccurate due to beats from degenerate and many close-lying frequencies.