The electron-capture and +-decay branchings (EC/+) and delayed proton decays of A=142 isotopes with 61 Z 66 and A=140 isotopes with 63 Z 65 were investigated with the OASIS facility on-line at the Lawrence Berkeley Laboratory SuperHILAC. Electron capture and positron-decay emission probabilities have been determined for Pm142 and Sm142 decays, and extensive decay schemes have been constructed for Eug142(2.34±0.12 s), Gd142(70.2±0.6 s), Eu140(1.51±0.02 s), and Gd140(15.8±0.4 s). Decay schemes for the new isotopes Tbg142(597±17 ms), Tbm142(303±17 ms), Dy142(2.3±0.3 s), Eum140(125±2 ms), and Tb140(2.4±0.2 s) are also presented. We have assigned rays to these isotopes on the basis of and x coincidences, and from half-life determinations. Electron-capture and +-decay branchings were measured for each decay, and -delayed proton branchings were determined for Dy142, Tb142, and Tb140 decays. QEC values, derived from the measured EC/+ branchings and the level schemes are compared with those from the Wapstra and Audi mass evaluation and the Liran and Zeldes mass calculation. The systematics of the N=77 isomer decays are discussed, and the intense 01+ and 10+ ground-state beta decays are compared with shell-model predictions for simple spin-flip transitions.
ASJC Scopus subject areas
- Nuclear and High Energy Physics