Expérience GANIL/SPIRAL/MUST2/E525SThe low-lying spectroscopy of 6He was investigated via the 2-neutron transfer reaction p(8He, t) with the 8He beam delivered by the SPIRAL facility at 15.4 A MeV. The light charged particles produced by the direct reactions were measured using the MUST2 Si-strip telescope array. Above the known 2+ state, two new resonances were observed: at E∗ = 2.6±0.3 MeV (width Γ = 1.6±0.4 MeV) and at 5.3±0.3 MeV with Γ = 2 ± 1 MeV. Through the analysis of the angular distributions, they correspond to a 2+ state and to an L = 1 state, respectively. These new states, challenging the nuclear theories, could be used as benchmarks for checking the microscopic inputs of the newly improved structure models, and should trigger development of models including the treatments of both core excitation and continuum coupling effects
We report on the g-factor measurement of the first isomeric state in (16)43S27 [Ex=320.5(5) keV, T1/2=415(5) ns, and g=0.317(4)]. The 7/2- spin-parity of the isomer and the intruder nature of the ground state of the nucleus are experimentally established for the first time, providing direct and unambiguous evidence of the collapse of the N=28 shell closure in neutron-rich nuclei. The shell model, beyond the mean-field and semiempirical calculations, provides a very consistent description of this nucleus showing that a well deformed prolate and quasispherical states coexist at low energy.
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