Gamma-Gamma Directional Correlations inNd147

Abstract

Directional correlation measurements have been made on the 320- to 92-kev and 280-to 320-kev gamma-ray cascades in ${\mathrm{Pm}}^{147}$ following the decay of 11.1-day ${\mathrm{Nd}}^{147}$ with a coincidence scintillation spectrometer using NaI detectors. The observed correlation functions are: $W\left(\theta \right)=1-(0.1030\mathrm{}\pm 0.0298)$ $P_2\left(cos\theta \right)+(0.0107\mathrm{}\pm 0.0099)$ $P_4\left(cos\theta \right)$, and $W\left(\theta \right)=1+(0.0710\mathrm{}\pm 0.0162)$ $P_2\left(cos\theta \right)-(0.0126\mathrm{}\pm 0.0103)$ $P_4\left(cos\theta \right)$, respectively, for the two cascades. The energy levels of ${\mathrm{Pm}}^{147}$ at ground state, 92 kev, 410 kev, and 690 kev were found to be ${\frac{7}{2}}^{+}$, ${\frac{7}{2}}^{+}$, ${\frac{7}{2}}^{+}$, and ${\frac{5}{2}}^{+}$, respectively. It was found that the 92-kev gamma ray has a mixture of (95±2)% $M1\mathrm{}$ and (5±2)% $E2\mathrm{}$ with ${\delta }_{92}=+(0.229\mathrm{}\pm 0.143)$, the 320-kev gamma ray has a mixture of 1% $M1\mathrm{}$ and 99% $E2\mathrm{}$ with ${\delta }_{320}=+9.95\mathrm{}\pm 0.11$, and the 280-kev gamma ray has a mixture of 99% $M1\mathrm{}$ and 1% $E2\mathrm{}$ with ${\delta }_{280}=-0.11\mathrm{}\pm 0.11$.