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In this work we investigate the two-neutron decay of 13Li and of the excited states of 11Li populated via one-proton removal from 14Be and 12Be, respectively. A phenomenological model is used to describe the decay of 11Li and 13Li. While the first one displays important sequential components, the second one appears dominated by the direct two-neutron decay. A microscopic three-body model is used to extract information on the spatial configuration of the emitted neutrons before the decay and shows that the average distance between the neutrons increases going from 11Li to 13Li.

γ emission probabilities from unbound states in 78,80Se, populated by a neutron-transfer reaction (d,p) on 77,79Se nuclei in inverse kinematics, were measured by directly detecting reaction residues. Assuming the spin distribution at the respective excitation energy of the unbound state, the cross-sections of the 79Se(n,γ)80Se reaction were evaluated using the γ emission probabilities. The surrogate-ratio method with the experimental γ emission probabilities of 78,80Se was also employed to deduce the cross-sections of 79Se(n,γ) reaction by incorporating the theoretical evaluations of the neutron-capture reaction on the isomeric state in 77Se. Our two cross-sections are in good agreement with existing nuclear data compilations for the neutron-capture reaction on 79Se. The presented method contributes to the body of existing knowledge by providing approaches for determining the neutron capture cross-sections of radioactive nuclei at various neutron energies.

To search for low-energy resonant structures in isospin T=3/2 three-body systems, we have performed the experiments ^{3}H(t,^{3}He)3n and ^{3}He(^{3}He,t)3p at intermediate energies. For the 3n experiment, we have newly developed a thick Ti-^{3}H target that has the largest tritium thickness among targets of this type ever made. The 3n experiment for the first time covered the momentum-transfer region as low as 15  MeV/c, which provides ideal conditions for producing fragile systems. However, in the excitation-energy spectra we obtained, we did not observe any distinct peak structures. This is in sharp contrast to tetraneutron spectra. The distributions of the 3n and 3p spectra are found to be similar, except for the displacement in energy due to Coulomb repulsion. Comparisons with theoretical calculations suggest that three-body correlations exist in the 3n and 3p systems, although not enough to produce a resonant peak.

The structure and decay of the most neutron-rich beryllium isotope, ^{16}Be, has been investigated following proton knockout from a high-energy ^{17}B beam. Two relatively narrow resonances were observed for the first time, with energies of 0.84(3) and 2.15(5) MeV above the two-neutron decay threshold and widths of 0.32(8) and 0.95(15) MeV, respectively. These were assigned to be the ground (J^{π}=0^{+}) and first excited (2^{+}) state, with E_{x}=1.31(6)  MeV. The mass excess of ^{16}Be was thus deduced to be 56.93(13) MeV, some 0.5 MeV more bound than the only previous measurement. Both states were observed to decay by direct two-neutron emission. Calculations incorporating the evolution of the wave function during the decay as a genuine three-body process reproduced the principal characteristics of the neutron-neutron energy spectra for both levels, indicating that the ground state exhibits a strong spatially compact dineutron component, while the 2^{+} level presents a far more diffuse neutron-neutron distribution.

Background: Although Japan is a major endemic area for human T-lymphotropic virus type 1 (HTLV-1) and the virus has been well-studied in this region, there is limited research on HTLV-1 in surrounding regions. In this study, we determined the complete genome sequences of HTLV-1 strains isolated from Taiwan and Japan and investigated the geographic characteristics of molecular subgroups and substitution mutations to understand the spread of HTLV-1 and its correlation with human migration., Methodology/principal Findings: The complete genome sequences of 26 HTLV-1 isolates from Taiwan were determined using next-generation sequencing and were compared with those of 211 isolates from Japan in terms of subgroup and genetic mutations. In total, 15/26 (58%) isolates from Taiwan belonged to the transcontinental subgroup and 11/26 (42%) isolates belonged to the Japanese subgroup. The transcontinental subgroup was significantly more prevalent among Taiwanese isolates than Japanese isolates (58% vs 18%, P < 0.0001). The mutation rate for the complete HTLV-1 sequence was as low as 0.2%. On examining individual base substitutions, the G-to-A mutation was predominant. Bayesian phylogenetic tree analysis estimated the time to the most recent common ancestor for the transcontinental and Japanese subgroups to be 28447 years. The transcontinental subgroups from Taiwan and Japan appeared to form clusters according to their respective regions., Conclusions/significance: The transcontinental subgroup of HTLV-1 is predominant in Taiwan, while the Japanese subgroup is common in Japan. The difference in subgroup distribution may be attributed to the initial spread of the transcontinental subgroup in East Asia, followed by the influx of the Japanese subgroup., Competing Interests: The authors have declared that no conflict of interest exists., (Copyright: © 2024 Nozuma et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)