Simultaneous investigation of the T=1(Jπ=0+) and T=0(J

Abstract

Simultaneous investigation of the T = 1 (J π = 0 + ) and T = 0 (J π = 9 + ) β decays in The β decay of the odd-odd nucleus 70 Br has been investigated with the BigRIPS and EURICA setups at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. The T = 0 (J π = 9 + ) and T = 1 (J π = 0 + ) isomers have both been produced in in-flight fragmentation of 78 Kr with ratios of 41.6(8)% and 58.4(8)%, respectively. A half-life of t 1/2 = 2157 +53 −49 ms has been measured for the J π = 9 + isomer from γ-ray time decay analysis. Based on this result, we provide a new value of the half-life for the J π = 0 + ground state of 70 Br, t 1/2 = 78.42 ± 0.51 ms, which is slightly more precise, and in excellent agreement, with the best measurement reported hitherto in the literature. For this decay, we provide the first estimate of the total branching fraction decaying through the 2 + 1 state in the daughter nucleus 70 Se, R(2 + 1 ) = 1.3 ± 1.1%. We also report four new low-intensity γ-ray transitions at 661, 1103, 1561, and 1749 keV following the β decay of the J π = 9 + isomer. Based on their coincidence relationships, we tentatively propose two new excited states at 3945 and 4752 keV in 70 Se with most probable spins and parities of J π = (6 + ) and (8 + ), respectively. The observed structure is interpreted with the help of shell-model calculations, which predict a complex interplay between oblate and prolate configurations at low excitation energies.

Mass measurements of As, Se, and Br nuclei, and their implication on the proton-neutron interaction strength toward the N=Z line

“…Since the measurements of Ref. [8] are accurate enough and not under dispute, the source of this discrepancy must lie in its mass value. The mass measurement of Ref.…”

“…However, the Ft value of 70 Br that is derived from its precise half-life and decay branching ratio [8] and only direct mass measurement (Penning trap [9]) deviates by approximately 12σ from the world average. Since the measurements of Ref.…”

“…Actually, the Penning trap result was derived from measuring the mass of the 70m Br isomer (t 1/2 = 2.2 s) and subtracting its known excitation energy, because the cycle time employed in the measurement [9] was much longer compared to the halflife of the nuclide 70 Br ((78.42 ± 0.51) ms [8]). Therefore, the Penning trap measurement of Ref.…”

Mass measurements of As, Se and Br nuclei and their implication on the proton-neutron interaction strength towards the N=Z line

“…However, the F t-value of 70 Br that is derived from its precise half-life and decay branching ratio [8] and only direct mass measurement (Penning trap [9]) deviates by approximately 12σ from the world average. Since the measurements of ref.…”

“…Since the measurements of ref. [8] are accurate enough and not under dispute, the source of this discrepancy is its mass value. The mass measurement of ref.…”