Five-body resonances of 8He using the complex scaling method

Abstract

The 0+ states of 8He are studied in a five-body 4He+n+n+n+n cluster model. Many-body resonances are treated on the correct boundary condition as Gamow states using the complex scaling method. The 0+_2 state of 8He is predicted as a five-body resonance in the excitation energy of 6.3 MeV with a width of 3.2 MeV, which mainly has a (p_{3/2})^2(p_{1/2})^2 configuration. In this state, number of the 0+ neuron pair shows almost two, which is different from the ground state having a large amount of the 2+ pair component. The monopole transition of 8He from the ground state into the five-body unbound states is also evaluated. It is found that the 7He+n component mostly exhausts the strength, while the 0+_2 contribution is negligible. The final states are dominated by 6He+n+n, not 4He+n+n+n+n. The results indicate the sequential breakup process of 8He to 7He+n to 6He+n+n by the monopole excitation.Comment: 6 pages, 6 figures, table I is updated for the experimental value

Four-body resonances of7B using the complex scaling method

“…In COSM, the effects of all open channels are taken into account explicitly [19] so that we can treat the manybody decay phenomena. In our previous work on neutron-rich systems [19][20][21], we successfully described He isotopes with the 4 He + 4n model up to the five-body resonances of 8 He, including full couplings with 5,6,7 He. We described many-body resonances using the complex scaling method (CSM) [22][23][24] under correct boundary conditions for all decay channels.…”

“…In CSM, the resonant wave functions are directly obtained by diagonalization of the complex-scaled Hamiltonian using L 2 basis functions. Results for light nuclei using CSM have been obtained successfully for energies, decay widths, and spectroscopic factors, and also for breakup strengths induced by Coulomb excitations [25,26], monopole transition [21] and one-neutron removal [20]. Recently, CSM has been developed to include nuclear reaction methods such as scattering amplitude calculation [27], the Lippmann-Schwinger equation [28], and the continuum-discretized coupled-channel (CDCC) method [29].…”

Five-body resonances of8C using the complex scaling method

“…In the 2p2h components, the p 1/2 and d 5/2 orbits contribute to the ground state. These results mean that the jj -coupling scheme and the p 3/2 subclosed nature are well established in the ground state of 8 C. To see the mirror symmetry, the results of the 8 He ground state described in the 4 He + 4n model [24] are shown in Table II. In the 8 He ground state, the extra four neutrons dominantly occupy the p 3/2 orbit with a squared amplitude of 0.86 and the 2p2h components are mixed by about 0.14.…”

“…In addition, it is important to reproduce the threshold energies of subsystems for particle decays, namely the positions of open channels. Emphasizing these theoretical conditions, in this study, we employ the cluster orbital shell model (COSM) [14,[20][21][22][23][24] of the 4 He + 4p five-body system. In COSM, the effects of all open channels are taken into account explicitly [22] so we can treat the many-body decaying phenomena.…”

“…In COSM, the effects of all open channels are taken into account explicitly [22] so we can treat the many-body decaying phenomena. In our previous works of neutron-rich systems [22][23][24], we have successfully described the He isotopes with the 4 He + 4n model up to the five-body resonances of 8 He, including the full couplings with 5,6,7 He. We have described many-body resonances using the complex scaling method (CSM) [25][26][27] under the correct boundary conditions for all decay channels.…”