Five-body resonances in He8 and C8 using the complex scaling method

Abstract

We study many-body resonances in the neuron-rich 8 He and the mirror proton-rich 8 C using the 4 He +N + N + N + N five-body model with the isospin T = 2 system. Resonances are described with the complex energy eigenvalues as the Gamow states using the complex scaling method. In 8 He, we obtain five states in which four states are resonances, and in 8 C all five states are resonances. We discuss the isospin-symmetry breaking dynamically induced by the Coulomb interaction in the energy spectra and decay widths of the resonances in two mirror nuclei. We predict the resonance energies and decay widths for the future experiments. We also investigate the configurations of valence nucleons above 4 He in two nuclei with the j j coupling scheme, and all the states dominantly have the p-shell configurations. From the configuration mixing, 8 He and 8 C give the similar results, which indicates the good symmetry in two nuclei.

Soft dipole resonance in neutron-rich 8He

“…These values are consistent with the recent experimental report of the corresponding energy 0.43(6) Fig. 2 Energy levels of 4−8 He measured from the 4 He energy [21]. Units are in MeV.…”

“…In our previous work [21], we predicted four resonances of 8 He with positive parity in the low excitation energy and the lowest resonance is the 2 + state, whose energy and decay width are consistent with the recent experimental data [15]. In our recent letter [22], we predicted the soft dipole mode of 8 He (1 − ) in the electric dipole strength, which makes a mild peak at the excitation energy of 13 MeV.…”

“…We start to discuss the results of the energy spectra of He isotopes to show the validity of the COSM with the complex scaling, the main parts of which are already reported in the previous work [21]. The energy spectra are useful to confirm the threshold energies of the multineutron emissions in the dipole transition of 8 He.…”

“…We use the 173.7 MeV of the repulsive strength of the Minnesota potential v N N instead of the original 200 MeV to reproduce 0.975 MeV of the two-neutron separation energy of 6 He. This condition is the same as used in the previous works [18,19,21,22] and gives a nice reproduction of the energy levels of He isotopes and their mirror nuclei.…”

“…So far, we have performed the analysis of the neutron-rich He isotopes and their mirror proton-rich unbound nuclei in the 4 He+N + N + N + N five-body cluster model, where 4 He is treated as an inert core [18][19][20][21][22]. We solve the motion of multi valence-nucleons around the 4 He core in the cluster orbital shell model (COSM) [23][24][25][26].…”