Angular Correlation Measurements inTe121andTe123

Abstract

Measurements of the angular correlation of the two-step transition in ${\mathrm{Te}}^{121}$ and ${\mathrm{Te}}^{123}$ have been made using a thin Te source (<1μg/${\mathrm{cm}}^2$). $K$ conversion electron-gamma, $L$ conversion electron-gamma and $K$ conversion-$K$ conversion cascades were investigated in both isomers using a thin lens beta spectrometer as the fixed detector and scintillation counters for the movable detector. The measured correlation was found to be of the form $1+A_2{P}_2\left(cos\theta \right)$ in agreement with the theoretically predicted angular correlation for the known spin sequence in the tellurium isomers ($\frac{11}{2}\to \frac{3}{2}\to \frac{1}{2}$). The measured values of $A_2$ corrected for geometry are -0.097±0.004, -0.092±0.009, -0.06±0.03 for the $K-\gamma$, $L-\gamma$, and $K-K$ cascades respectively in ${\mathrm{Te}}^{123}$ and -0.015±0.007, -0.007±0.007, and -0.10±0.04 for the same cascades in ${\mathrm{Te}}^{121}$. Comparison of the results of the $K-\gamma$ cascades with theory shows that the second transition is a mixture of (1.3±0.1) percent $E2\mathrm{}$ and 98.7 percent $M1\mathrm{}$ in ${\mathrm{Te}}^{123}$ and (5.6±0.5) percent $E2\mathrm{}$ and 94.4 percent $M1\mathrm{}$ in ${\mathrm{Te}}^{121}$. The ratio of reduced matrix elements is plus in both cases using the Biedenharn and Rose notation. The results for the $K-K$ angular correlation are consistent with the $K-\gamma$ correlations and are used to prove that the correlations, which are smaller than the $M4-M1\mathrm{}$ correlation, cannot result from reduction of the $M4-M1\mathrm{}$ correlation by the action of extra-nuclear fields.