Decay Properties of Neutron-Deficient Osmium and Rhenium Isotopes. II. TheA=180Decay Chain

The decay properties of ${\mathrm{Os}}^{180}$ and ${\mathrm{Re}}^{180}$ have been investigated using Ge(Li), anthracene, and NaI(Tl) detectors in singles and coincidence measurements. A solvent extraction method for rapid milking of daughter rhenium activities from osmium was used to confirm the genetic relationship between 21.5-min ${\mathrm{Os}}^{180}$ and 2.45-min ${\mathrm{Re}}^{180}$. No radiations other than $K$ x rays were detected in ${\mathrm{Os}}^{180}$ decay and it is concluded that this isotope decays by electron capture with a $log\mathrm{ft}$ value in the range 4.7±0.3 In ${\mathrm{Re}}^{180}$ decay the following radiations were identified: $K$ x rays (105), $\gamma$ rays of energies 103.6±0.3 (26), 232.6±1.0 (1.2), 750.8±1.0 (0.8), 826.4±0.8 (11), and 902.2±0.5 keV (100), and a single positron group of endpoint 1.76±0.4 MeV (8). Relative intensities are given in parentheses. A ${\mathrm{Re}}^{180}$ decay scheme which is consistent with all the observations, including $\gamma -\gamma$ coincidence measurements, is proposed; its most interesting feature is a two-quasi-particle state ($J^{\pi }=2^{-}$) at 1006 keV, which de-excites almost exclusively to the first excited state of ${\mathrm{W}}^{180}$. The disintegration energy of ${\mathrm{Re}}^{180}$ was determined to be 3.78±0.04 MeV.