Radioactive Decay of 65-HourSb122

Physical Review1955Vol. 98(3), pp. 645–652

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Abstract

65-hour ${\mathrm{Sb}}^{122}$ was investigated by using ${\mathrm{Sb}}^{121}$ (97.7 percent-99.4 percent) that had been bombarded with thermal neutrons for 70 hours. Spectrometer measurements show three beta groups with end-point energies: 1.987, 1.423, and 0.734 Mev; and $log\mathrm{ft}$ values: 8.6 [$logft({w}^{2}\ensuremath{-}m{c}^{2})=10.0$, ${p}^{2}+{q}^{2}$ shape], 7.6 (allowed shape), and 7.7; and four gamma rays with energies: 0.563, 0.693, 1.152, and 1.256 Mev; and intensities: 73 percent, 3.6 percent, 0.75 percent and 0.8 percent. From gamma-gamma and beta-gamma coincidences the excited states of ${\mathrm{Te}}^{122}$ were found at 0.563 and 1.256 Mev. X-gamma coincidences and x-ray critical absorption showed 2.2 percent and 0.8 percent $K$-capture transitions to the ground state and to a 1.152-Mev level in ${\mathrm{Sn}}^{122}$. The $\mathrm{ft}$ values for the transitions to ${\mathrm{Sn}}^{122}$ are 13 times smaller than the corresponding transitions to ${\mathrm{Te}}^{122}$. Annihilation radiation was not observed setting an upper limit of 0.005 percent for positrons. The directional correlation of the 0.693- and the 0.563-Mev gamma rays indicated a 2-2-0 cascade, with the 2-2 transition 91+5 percent quadrupole. The first excited state in ${\mathrm{Te}}^{122}$ was also shown to be 2+ from a measurement of the $K$ conversion coefficient of the 0.563-Mev gamma ray. We conclude therefore that the ground state of ${\mathrm{Sb}}^{122}$ is 2- (${g}_{\frac{7}{2}}, {h}_{\frac{11}{2}}$), the first two excited states of ${\mathrm{Te}}^{122}$ are 2+, and the first excited state of ${\mathrm{Sn}}^{122}$ may also be 2+.

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Abstract

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