Neutron transition strengths of21+states in the neutron-rich oxygen isotopes determined from inelastic proton scattering

Abstract

A coupled-channel analysis of the 18,20,22 O(p, p ) data has been performed to determine the neutron transition strengths of the 2 + 1 states in oxygen targets, using the microscopic optical potential and inelastic form factor calculated in the folding model. A complex density-and isospin-dependent version of the CDM3Y6 interaction was constructed, based on the Brueckner-Hartree-Fock calculation of nuclear matter, for the folding model input. Given an accurate isovector density dependence of the CDM3Y6 interaction, the isoscalar (δ 0 ) and isovector (δ 1 ) deformation lengths of the 2 + 1 states in 18,20,22 O have been extracted from the folding model analysis of the (p, p ) data. A specific N dependence of δ 0 and δ 1 has been established which can be linked to the neutron shell closure occurring at N approaching 16. The strongest isovector deformation was found for the 2 + 1 state in 20 O, with δ 1 about 2.5 times larger than δ 0 , which indicates a strong core polarization by the valence neutrons in 20 O. The ratios of the neutron/proton transition matrix elements (M n /M p ) determined for the 2 + 1 states in 18,20 O have been compared with those deduced from the mirror symmetry, using the measured B(E2) values of the 2 + 1 states in the proton-rich 18 Ne and 20 Mg nuclei, to discuss the isospin impurity in the 2 + 1 excitation of the A = 18, T = 1 and A = 20, T = 2 isobars.

Extended Hartree-Fock study of the single-particle potential: The nuclear symmetry energy, nucleon effective mass, and folding model of the nucleon optical potential

“…(22). At variance with the g(E) factor fixed by the incident energy [18,19], g k(E, ρ) is now a momentum dependent function (see Fig.…”

“…These medium effects are usually considered as the main physics origin of an explicit density dependence embedded in the different versions of the effective NN interaction, being used currently in the HF calculations of the nuclear structure or nuclear reaction studies. Among them, quite popular are the density dependent versions of the M3Y interaction (originally constructed to reproduce the G-matrix elements of the Reid [11] and Paris [12] NN potentials in an oscillator basis), which have been successfully used in the HF studies of the NM [13][14][15][16][17] as well as in the folding model studies of the nucleon-nucleus and nucleus-nucleus scattering [18][19][20][21][22][23].…”

Equation of state of neutron star matter, and the nuclear symmetry energy

“…In attempt to find a realistic version of the effective NN interaction for consistent use in the mean-field studies of NM and finite nuclei as well as in the nuclear reaction calculations, we have performed recently a systematic HF study of NM [23] using the CDM3Yn interactions, which have been used mainly in the folding model studies of the nuclear scattering [14,15,21,22], and the M3Y-Pn interactions carefully parametrized by Nakada [17][18][19] for use in the HF studies of nuclear structure. For comparison, the same HF study has also been done with the D1S and D1N versions of the Gogny interaction [24,25] and Sly4 version of the Skyrme interaction [26].…”

“…These density dependent versions of the M3Y interaction have been used in the nonrelativistic Hartree-Fock (HF) studies of symmetric and asymmetric NM. Some of them have been successfully used in the folding model studies of the nucleon-nucleus and nucleus-nucleus scattering [13][14][15][20][21][22].…”

Rearrangement term in the nonlocal folding model of the nucleon optical potential

“…These in-medium effects are effectively taken into account by the density dependence explicit embedded in different versions of the effective NN interaction used in the nuclear structure and nuclear reactions studies. In the present work, we focus on the CDM3Yn density dependent versions [14] of the M3Y-Paris interaction [15] which have been successfully used in the HF studies of NM [6,7,16,17,18] as well as in the folding model calculation of the nucleon and nucleus-nucleus OP [11,12,14,19,20,21]. In general, the folding model calculation of the nucleon OP is done on the HF level, and the folded OP lacks, therefore, the higher-order rearrangement term that arises naturally in the Landau theory of infinite Fermi systems [22].…”