The disintegration of ${\mathrm{Cs}}^{130}$ (30 min) has been studied with the help of a magnetic lens spectrometer and a NaI(Tl) scintillation spectrometer. ${\mathrm{Cs}}^{130}$ decays to both ${\mathrm{Xe}}^{130}$ by positron emission and $K$ electron capture and to ${\mathrm{Ba}}^{130}$ by negatron emission. The end-point energy of the positrons is 1.97 Mev and of the negatrons 0.442 Mev. Since no gamma-rays other than annihilation radiation were observed, it is assumed that the disintegration leads to the ground state of both ${\mathrm{Xe}}^{130}$ and ${\mathrm{Ba}}^{130}$.

• Received 16 April 1952

DOI:https://doi.org/10.1103/PhysRev.87.454