Directional Correlation of Gamma Transitions in Promethium-147

Abstract

The angular correlations of five different gamma-ray cascades, involving the states of ${\mathrm{Pm}}^{147}$, excited in the decay of ${\mathrm{Nd}}^{147}$, have been studied. The observed correlation functions for the various cascades are as follows: $W\left({}_{599}{}^{}{}_{}{}^{}\theta _{91}^{}{}_{}{}^{}\right)=1+(0.056\mathrm{}\pm 0.028)P_2\left(cos\theta \right)-(0.049\mathrm{}\mp 0.034)P_4\left(cos\theta \right);$ $W\left({}_{442}{}^{}{}_{}{}^{}\theta _{91}^{}{}_{}{}^{}\right)=1+(0.065\mathrm{}\pm 0.020)P_2\left(cos\theta \right)-(0.035\mathrm{}\mp 0.025)P_4\left(cos\theta \right);$ $W\left({}_{199}{}^{}{}_{}{}^{}\theta _{400}^{}{}_{}{}^{}\right)=1-(0.054\mathrm{}\pm 0.020)P_2\left(cos\theta \right)+(0.043\mathrm{}\mp 0.025)P_4\left(cos\theta \right);$ $W\left({}_{199}{}^{}{}_{}{}^{}\theta _{491}^{}{}_{}{}^{}\right)=1+(0.095\mathrm{}\pm 0.028)P_2\left(cos\theta \right)+(0.014\mathrm{}\mp 0.034)P_4\left(cos\theta \right);$ and $W\left({}_{120}{}^{}{}_{}{}^{}\theta _{322}^{}{}_{}{}^{}\right)=1+(0.035\mathrm{}\pm 0.020)P_2\left(cos\theta \right)-(0.001\mathrm{}\mp 0.025)P_4\left(cos\theta \right).\mathrm{}$ The analysis of the above correlation functions with the ground-state spin of ${\mathrm{Pm}}^{147}$ as $\frac{7}{2}$, and the consideration of the $log\mathrm{ft}$ values for the beta transitions from ${\mathrm{Nd}}^{147}$ state of spin $\frac{5}{2}$, give the spin values for the 91, 413, 491, 533, and 690-kev excited states as $\frac{5}{2}$, $\frac{7}{2}$, $\frac{7}{2}$, $\frac{5}{2}$, and $\frac{5}{2}$, respectively. The data of Bishop et al. and Ambler et al. on nuclear alignment experiments have been reanalyzed. The results are consistent with the above spin assignment of $\frac{5}{2}$ for both the 91- and 533-kev levels.