Neutron-Deficient Members of theA=139Decay Chain. II. 4.5-hPr139

Abstract

The $\gamma$ rays emitted following the decay of 4.5-h ${\mathrm{Pr}}^{139}$ have been investigated with Ge(Li) and NaI(Tl) detectors in singles and anticoincidence configurations. Twelve transitions having the following energies (and relative intensities) were observed: 254.7 (53), 1320.0 (13), 1347.4 (≡100), 1375.7 (33), 1563.6 (9), 1596.6 (10), 1630.6 (70), 1653.3 (8), 1730.2 (1.6), 1818.4 (7.0), 1907.9 (3.5), and 2015.9 keV (3.0). Using energy sums and the anticoincidence results, we placed states in ${\mathrm{Ce}}^{139}$ at $0 (\frac{3}{2}+)$, 254.7 (½+), $1320.0 (\frac{3}{2},\frac{5}{2},\frac{7}{2})$, $1347.4 (\frac{7}{2}+)$, $1596.6 (\frac{3}{2},\frac{5}{2},\frac{7}{2})$, $1630.6 (\frac{3}{2},\frac{5}{2}+)$, $1818.4 (\frac{3}{2},\frac{5}{2}+)$, $1907 (\frac{3}{2},\frac{5}{2}+)$, $1984.9 (\frac{3}{2},\frac{5}{2}+)$, and $2015.9 \mathrm{keV} (\frac{3}{2},\frac{5}{2},\frac{7}{2}+)$. The assignments were made on the basis of $log\mathrm{ft}$ values and relative photon intensities. The single particle versus collective behavior of the states is also discussed.