Quadrupole collectivity in island-of-inversion nuclei28,30Neand34,36Mg

Abstract

The quadrupole collectivity of neutron-rich even-even neon and magnesium nuclei around N = 20, 28,30 Ne,and 32,34,36 Mg, was studied via proton inelastic scattering on a liquid hydrogen target by in-beam γ -ray spectroscopy in inverse kinematics. The angle-integrated cross sections for the first 2 + states of these nuclei were determined by measuring de-excitation γ rays. The deformation lengths were extracted from the angle-integrated cross sections using distorted-wave calculations. The deformation length of 30 Ne (δ (p,p ) = 1.59 +0.08 −0.09 fm) is smaller than that of 32 Mg (1.83 +0.10 −0.11 fm), which exhibits the largest quadrupole collectivity among the neutron-rich N = 20 isotones. Along the magnesium isotopic chain, the deformation lengths of 34 Mg and 36 Mg were deduced to be 2.30 +0.09 −0.10 fm and 1.90 +0.16 −0.17 fm, respectively. The evolution of quadrupole deformation in the vicinity of 32 Mg is discussed by comparing the present results with the theoretical calculations.

Mapping the deformation in the “island of inversion”: Inelastic scattering ofNe30andMg36at intermediate energies

“…It is noted that the deformation length from scattering on hydrogen obtained in Ref. [29] of δ = 1.90(22) fm for 36 Mg agrees well with the present findings. However, the result of δ = 1.59 (11) fm obtained in the same work for 30 Ne is lower than the present findings for the carbon target.…”

“…Due to this robustness, an error of 5% was adopted for the choice of optical potential, which is comparable to the systematic error employed in Ref. [29] for the inelastic scattering on the hydrogen target. The assumption that δ C = δ N would result in an ∼8% higher B(E2)↑ value for 30 Ne and an ∼4% lower B(E2)↑ value for 36 Mg.…”

“…A first experimental hint in this direction was given by the increased nuclear deformation lengths (δ N ) observed in Refs. [21,29], suggesting large quadrupole deformation parameters (β 2 , in the following abbreviated as β and distinguished as β N and β C for nuclear and electromagnetic parameters). The present work reports on Coulomb-and nuclear-force-dominated inelastic scattering measurements of 30 Ne and 36 Mg in order to further elucidate the B(E2)↑ and deformation pattern in both isotopic chains at and beyond N = 20.…”

Nuclear-structure studies of exotic nuclei with MINIBALL

“…The results on transition strengths brings in an additional sensitive probe to test residual interactions [20]. Sub-barrier CE was also performed on a mixed beam of 62 Mn and 62 Fe. Here a new transition in 62 Mn was found at 418 keV, which has been tentatively associated to a  is in good agreement with the value measured at intermediate energy confirming the low  + + 0 2 1 1 transition probability [19].…”

“…Sub-barrier CE was also performed on a mixed beam of 62 Mn and 62 Fe. Here a new transition in 62 Mn was found at 418 keV, which has been tentatively associated to a  is in good agreement with the value measured at intermediate energy confirming the low  + + 0 2 1 1 transition probability [19]. Future safe CE experiments on more neutron-rich nickel isotopes are not hindered by the in-target production using proton-induced fission but by the slow release out of the target matrix and by potential contamination of gallium isobars.…”