부산대학교 도서관

The first direct determination of the ground-state-to-ground-state β-777777γ77-→77∗+β-σ977≈-decay Q-value of β-777777γ77-→77∗+β-σ977≈As to β-777777γ77-→77∗+β-σ977≈Se was performed by measuring their atomic mass difference utilizing the double Penning trap mass spectrometer, JYFLTRAP. The resulting Q-value is 684.463(70) keV, representing a remarkable 24-fold improvement in precision compared to the value reported in the most recent Atomic Mass Evaluation (AME2020). With the significant reduction of the uncertainty of the ground-state-to-ground-state Q-value and knowledge of the excitation energies in β-777777γ77-→77∗+β-σ977≈Se from β-777777γ77-→77∗+β-σ977≈-ray spectroscopy, the ground-state-to-excited-state Q-value of the transition β-777777γ77-→77∗+β-σ977≈As (3/2β-777777γ77-→77∗+β-σ977≈, ground state) β-777777γ77-→77∗+β-σ977≈β-777777γ77-→77∗+β-σ977≈Seβ-777777γ77-→77∗+β-σ977≈ (5/2β-777777γ77-→77∗+β-σ977≈, 680.1035(17) keV) was refined to be 4.360(70) keV. We confirm that this potential low Q-value β-777777γ77-→77∗+β-σ977≈-decay transition for neutrino mass determination is energetically allowed at a confidence level of about 60β-777777γ77-→77∗+β-σ977≈. Nuclear shell-model calculations with two well-established effective Hamiltonians were used to estimate the partial half-life for the low Q-value transition. The half-life was found to be of the order of 10β-777777γ77-→77∗+β-σ977≈ years for this first-forbidden non-unique transition. Since the half-life of β-777777γ77-→77∗+β-σ977≈As is only β-777777γ77-→77∗+β-σ977≈ 2 days, usage of it as source for rare-event experiments searching for the electron antineutrino mass would be challenging.