Fast-timing study of the l-forbidden 1/2+→3/2+ M1 transition in Sn129

Journal article

The levels in 129Sn populated from the 𝛽− decay of 129In isomers were investigated at the ISOLDE facility of CERN using the newly commissioned ISOLDE Decay Station (IDS). The lowest 1/2+ state and the 3/2+ ground state in 129 Sn are expected to have configurations dominated by the neutron 𝑠1/2 (𝑙=0) and 𝑑3/2 (𝑙=2) single-particle states, respectively. Consequently, these states should be connected by a somewhat slow 𝑙-forbidden 𝑀⁢1 transition. Using fast-timing spectroscopy we have measured the half-life of the 1/2+ 315.3-keV state, 𝑇1/2= 19(10) ps, which corresponds to a moderately fast 𝑀⁢1 transition. Shell-model calculations using the CD-Bonn effective interaction, with standard effective charges and 𝑔 factors, predict a 4-ns half-life for this level. We can reconcile the shell-model calculations to the measured 𝑇1/2 value by the renormalization of the 𝑀⁢1 effective operator for neutron holes.

Authors: Lică, R; Mach, H; Fraile, LM; Gargano, A; Borge, MJG

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review C
• Volume: 93
• Issue: 4
• Article number: 44303
• Publication date: 2016-04-04
• DOI: 10.1103/physrevc.93.044303
• EISSN: 2469-9993
• ISSN: 2469-9985
• Language: English
• Keywords: isomer decays; radiation detectors; 90 ≤ A ≤ 149; electromagnetic transitions; radioactive beams; lifetimes & widths; beta decay; shell model