Beta-Gamma Directional Correlation inEu154

Abstract

The energy dependence of the beta-gamma angular correlation between the outer beta-ray group of ${\mathrm{Eu}}^{154}$, $W_0=1.86\mathrm{}$ Mev, and the 123-kev gamma ray of the daughter ${\mathrm{Gd}}^{154}$ has been measured with a shaped magnetic field beta-gamma coincidence spectrometer. A negative correlation coefficient, accurate to about 5%, is obtained which ranges from -0.10 to -0.17 in the energy region 0.80 to 1.60 Mev. It is shown that the modified $B_{\mathrm{ij}}$ approximation must be relaxed to explain the data. The nuclear parameters (Kotani's notation) which result are: $x=-0.24\mathrm{}\pm 0.05$, $u=+0.05\mathrm{}\pm 0.03$, $Y=+0.76\mathrm{}\pm 0.08$. These values are compared with those which have been reported for ${\mathrm{Eu}}^{152}$: $x=u=0\mathrm{}$, $Y=0.69\mathrm{}\pm 0.06$.