Internal-Conversion-Electron Study of the Decay ofBa133toCs133

Abstract

The 40- to 500-keV region of the internal-conversion-electron spectrum from the decay of ${\mathrm{Ba}}^{133}$ has been investigated with an iron-core, $\pi \sqrt{2}$ double-focusing spectrometer. Transitions of 383.79(7), 355.92(6), 302.78(5), 276.35(5), 223.15(5), 160.58(4), 80.990(22), 79.622(18), and 53.152(20) keV have been observed, and their multipolarities have been determined from measurements of the conversion-electron intensity ratios— $\frac{L_1}{\frac{L_2}{L_3}}$ and/or $\frac{K}{L}$. No new lines with intensity greater than 2.3% of the $356K$ line were found. The $437K$ line was found to have an intensity less than 0.01% of the $356K$ line. The multipolarities obtained for the nine observed transitions were compared with previous measurements of ${\alpha }_K$ and $\gamma -\gamma$ angular correlations. This comparison resulted in unique spin-parity assignments of ${\frac{7}{2}}^{+}$, ${\frac{5}{2}}^{+}$, ${\frac{5}{2}}^{+}$, ${\frac{3}{2}}^{+}$, and ${\mathrm{½}}^{+}$ for the ground state and the 80.997(6)-, 160.58(4)-, 383.79(7)-, and 436.93(6)-keV levels, respectively, in ${\mathrm{Cs}}^{133}$. The measurements of $\frac{K}{L_3}$ and $\frac{L_1}{L_3}$ for the 161-keV transition are consistent with previous 276-161 $\gamma -\gamma$ directional-correlation measurements only if penetration effects are included with a $\lambda$ value of 45±10 or 180±20, where $\lambda$ is defined as the ratio of the penetration matrix element to the normal $\gamma$-ray matrix element.