Gamma-Gamma Directional Correlation inPr143

Abstract

The directional correlations of four $\gamma -\gamma$ cascades in ${\mathrm{Pr}}^{143}$ fed from the decay of ${\mathrm{Ce}}^{143}$ have been studied. The correlation functions for the 293-57, 232-493, 591-293, and the 668-57-keV cascades are found to be: $W\left({\theta }_{293-57}\right)=1+(0.112\mathrm{}\pm 0.009)P_2\left(cos\theta \right)$, $W\left({\theta }_{232-493}\right)=1-(0.176\mathrm{}\pm 0.008)P_2\left(cos\theta \right)-(0.001\mathrm{}\pm 0.012)P_4\left(cos\theta \right)$, $W\left({\theta }_{591-293}\right)=1+(0.146\mathrm{}\pm 0.015)P_2\left(cos\theta \right)+(0.003\mathrm{}\pm 0.026)P_4\left(cos\theta \right)$, and $W\left({\theta }_{668-57}\right)=1+(0.063\mathrm{}\pm 0.018)P_2\left(cos\theta \right)$, respectively. Knowing the spin of the ground state of ${\mathrm{Pr}}^{143}$ as ${\frac{7}{2}}^{+}$ and the recently measured spin of the ground state of ${\mathrm{Ce}}^{143}$ as ${\frac{3}{2}}^{-}$, and from the analysis of the angular-correlation results combined with the $log\mathrm{ft}$ values of $\beta$ transitions from ${\mathrm{Ce}}^{143}$, the levels of ${\mathrm{Pr}}^{143}$ have been assigned spins and parities as follows: ground state, ${\frac{7}{2}}^{+}$; 57 keV, ${\frac{5}{2}}^{+}$; 351 keV, ${\frac{3}{2}}^{+}$; 493 keV, ${\frac{7}{2}}^{+}$; 725 keV, ${\frac{5}{2}}^{+}$; 942 keV, ${\frac{3}{2}}^{+}$ or ${\frac{5}{2}}^{+}$; 1160 keV, ${\mathrm{½}}^{+}$, ${\frac{3}{2}}^{+}$, or ${\frac{5}{2}}^{+}$; and 1395 keV, ${\frac{3}{2}}^{-}$ or ${\frac{5}{2}}^{-}$.