Jack R. MacDonald

A two-dimensional Doppler broadened technique in positron annihilation

Abstract A new two-dimensional positron annihilation technique has been developed which is capable of measuring positrons annihilating with deeply bound electrons. The technique features extremely low background and provides a √2 improvement in resolution over standard Doppler broadening systems. A basic description of the system is given and preliminary results are shown.

Lifetimes of 2+ states in 58Ni

Abstract The mean lifetimes of six 2 + states in 58 Ni have been measured by the Doppler shift attenuation method and 16 transition probabilities have been extracted. The results have been compared with some recent calculations of electromagnetic transition probabilities.

Electric monopole transitions in Ca 40

The E0 pair decay branching ratio (GAMMA/sub ..pi..//GAMMA) for the 5.21-MeV 0/sup +/ fifth excited state of /sup 40/Ca was measured. The state was excited by inelastic proton scattering. The e/sup -/-e/sup +/ pairs were detected in two ..delta..E-E scintillation telescopes in coincidence with backscattered protons. A branching ratio limit of 1.4 x 10/sup -3/ was determined which corresponds to a monopole strength rho .. 0/sup +//sub 2/)/(2/sup +//sub 2/ ..-->.. 0/sup +//sub 1/)) = (2.1 +- 0.1) x 10/sup -2/ for the decay of 5.25-MeV 2/sup +/ state was measured and corresponds to a B (E2) = (3.5 +- 0.6) e/sup 2/ fm/sup 4/. (AIP)

Electric monopole transitions in /sup 40/Ca. [E0 pair decay branching ratio]

The E0 pair decay branching ratio (GAMMA/sub ..pi..//GAMMA) for the 5.21-MeV 0/sup +/ fifth excited state of /sup 40/Ca was measured. The state was excited by inelastic proton scattering. The e/sup -/-e/sup +/ pairs were detected in two ..delta..E-E scintillation telescopes in coincidence with backscattered protons. A branching ratio limit of 1.4 x 10/sup -3/ was determined which corresponds to a monopole strength rho .. 0/sup +//sub 2/)/(2/sup +//sub 2/ ..-->.. 0/sup +//sub 1/)) = (2.1 +- 0.1) x 10/sup -2/ for the decay of 5.25-MeV 2/sup +/ state was measured and corresponds to a B (E2) = (3.5 +- 0.6) e/sup 2/ fm/sup 4/. (AIP)

The lattice location of fluorine in iron and nickel

Abstract The lattice location of implanted fluorine in iron and nickel crystals has been studied using the ion-beam particle channeling technique and proton-induced nuclear reactions in an attempt to determine lattice sites corresponding to measured magnetic hyperfine fields at fluorine in these ferromagnets.