Polarization Correlation Measurements onEu154

The spins and parities of the 1400- and 1723-kev levels in ${\mathrm{Gd}}^{154}$ are discussed on the basis of the polarization-directional correlation measurements on the 1277-123 and 725-998 kev gamma-gamma cascades following the $\beta$ decay of ${\mathrm{Eu}}^{154}$. In the case of the 1277-123-kev cascade, directional correlation measurements and the polarization correlation measurements of the 1277-kev gamma ray are made with liquid and solid sources. An attenuation in the anistropy of directional correlation and in the degree of linear polarization correlation has been observed in both the sources, the attenuation in the solid source being greater. In the 725-998 kev cascade, the polarization of either of the two radiations has been measured in two separate experiments. On the basis of these measurements, the spins and parities of both the 1400- and the 1723-kev levels in ${\mathrm{Gd}}^{154}$ are assigned $2^{-}$. The performance of the apparatus has been checked by measuring the polarization correlations of known cascades in ${\mathrm{Ni}}^{60}$, ${\mathrm{Ti}}^{46}$, ${\mathrm{Pd}}^{106}$, and ${\mathrm{Sr}}^{88}$.