Electron Capture Decay ofLu173to Levels inYb173

Abstract

The electron capture of ${\mathrm{Lu}}^{173}$ (1.30 yr) to levels in ${\mathrm{Yb}}^{173}$ has been investigated using scintillation spectrometers and permanent magnet spectrographs. Levels in ${\mathrm{Yb}}^{173}$ were observed at 78.7 ($\frac{7}{2}-$), 179.5 ($\frac{9}{2}-$), 351.2 ($\frac{7}{2}+$), and 636.8 ($\frac{7}{2}-$) kev. The first two excited states may be interpreted as members of a rotational band based on theg round state [(512) $\frac{5}{2}-$]. The levels at 351 and 637 kev are probably the intrinsic levels [(633) $\frac{7}{2}+$] and [(514) $\frac{7}{2}-$], respectively, predicted by Nilsson. $L$ electron capture was observed to be the primary mode of population of the 637-kev level. Relative reduced transition probabilities were obtained for all transitions to the ground-state rotational band, and comparisons with theoretical branching ratios were made. $\mathrm{Log}\mathrm{}\left(\mathrm{ft}\right)\mathrm{}$ values were estimated from the observed $K$-capture branching ratios.