EXPERIMENTAL INVESTIGATIONS ON ELECTRON CAPTURE DECAY OF MANGANESE 54 AND ZINC 65

The electron capture decay of Mn 54 and Zn 65 was investigated using Na I(Tl)-detectors. Spectroscopic-coincidence techniques were employed to examine the K-electron capture rates of Mn 54 and Zn 65, the branching ratio and positron rate of Zn 65. The experimental results are:Pkωk(Mn)=0.2492±0.0017, Pkωk(Zn)=0.3927±0.0026, EC*/EC0(Zn)=53.2±1.0/46.8±1.0, γ/β+=35.1±1.7, K0/β+=27.7±1.5. Thus electron capture to the excited state of Cu 65 occurs to the extent of 52.4±1.0% while electron capture and positron decay to the ground state were found to be associated with 46.1±1.0% and 1.49±0.05% of the disintegrations. These data partly disagree significantly from measurements of other authors. Using the fluorescence yields ωk(Cr)=0.279 and ωk(Cu)=0.4425, deduced from other measurements, values of L+M/K of electron capture to the excited state could be derived:L+M/K(Mn 54)=0.120±0.015 and L+M/K(Zn 65)=0.127±0.015. These ratios agree with the calculations of Bahcall. The half-lives of Mn 54 and Zn 65 have been determined to be T1/2(Mn 54)=312±5d, T1/2(Zn 65)=243±4 d The energy of the Zn 65-γ-rays was measured with a Ge(Li)-counter:Eγ=1115.5±0.5 keV. © 1968 Springer-Verlag.