New Chain Barium-126—Cesium-126

Abstract

The neutron-deficient chain ${\mathrm{Ba}}^{126}$-${\mathrm{Cs}}^{126}$ has been produced from nitrogen-ion bombardments of indium in the 60-inch cyclotron, by the reaction ${\mathrm{In}}^{115}(\mathrm{N}, 3n)$. Studies have been made of this new chain with a 50-channel scintillation spectrometer, a scintillation coincidence spectrometer, and a time-of-flight mass spectrograph. Element assignments and genetic relations have been verified chemically, and the mass number assigned with the isotope separator. ${\mathrm{Ba}}^{126}$ decays principally by orbital electron capture with a half-life of 96.5\ifmmode\pm\else\textpm\fi{}2.0 minutes, and its daughter ${\mathrm{Cs}}^{126}$ is a positron emitter of 1.6\ifmmode\pm\else\textpm\fi{}0.2 minute half-life and electron capture branching of 18\ifmmode\pm\else\textpm\fi{}4 percent. The decay of ${\mathrm{Cs}}^{126}$ proceeds by allowed transitions, \ensuremath{\sim}62 percent to the ground state of ${\mathrm{Xe}}^{126}$ and \ensuremath{\sim}38 percent to the first excited state at 385 kev. The positron spectrum has a maximum energy of 3.8\ifmmode\pm\else\textpm\fi{}0.4 Mev. On the basis of its decay properties, ${\mathrm{Cs}}^{126}$ appears to have a groundstate configuration of (1+).