Nuclear Levels ofCs133

The gamma rays of ${\mathrm{Cs}}^{133}$ following the electron-capture decay of ${\mathrm{Ba}}^{133}$ were studied using a coincidence scintillation spectrometer. Gamma rays with the following energies (in kev) were observed: 386, 356, 301, 276, (220), 162, 82, 80, and 54. The energies (in kev) of the nuclear levels of ${\mathrm{Cs}}^{133}$ with their spins and parities are: ground state ($\frac{7}{2}+$), 82 ($\frac{5}{2}+$), 162 ($\frac{3}{2}+$), 383 ($\frac{3}{2}+$), and 438 (½+). The electron-capture transitions and their relative intensities are as follows: (a) to the 438-kev level, 76% (b) to the 383-kev level, 11% (c) to the 162-kev level, 13%. In the decay of ${\mathrm{Xe}}^{133}$, (1.5±1.0)% of the beta transitions was observed to go to the 162-kev level in ${\mathrm{Cs}}^{133}$ and the remaining go to the 82-kev level.