A self-consistent study of multipole response in neutron-rich nuclei using a modified realistic potential

Abstract

Abstract. The multipole response of neutron rich O and Sn isotopes is computed in Tamm-Dancoff and random-phase approximations using the canonical Hartree-Fock-Bogoliubov quasi-particle basis. The calculations are performed using an intrinsic Hamiltonian composed of a V lowk potential, deduced from the CD-Bonn nucleon-nucleon interaction, corrected with phenomenological density dependent and spin-orbit terms. The effect of these two pieces on energies and multipole responses is discussed. The problem of removing the spurious admixtures induced by the center of mass motion and by the violation of the number of particles is investigated. The differences between the two theoretical approaches are discussed quantitatively. Attention is then focused on the dipole strength distribution, including the low-lying transitions associated to the pygmy resonance. Monopole and quadrupole responses are also briefly investigated. A detailed comparison with the available experimental spectra contributes to clarify the extent of validity of the two self-consistent approaches. ‡ present address : Ecole Normale Superieur (ENS) de Cachan, 61 av. du Président Wilson, Cachan -France Self-consistent study of multipole response in neutron rich nuclei using a modified realistic potential2

Dipole response in neutron-rich nuclei within self-consistent approaches using realistic potentials

“…As in [19], however, we found necessary to add a corrective density dependent piece in order to get single-particle spectra sufficiently compressed so as to reproduce the main peak of the experimental GDR. Using such a modified Hamiltonian, we obtained spectra qualitatively consistent with experiments for all light, medium mass and heavy isotopes [20].…”

“…[21,22], while V ρ is a corrective repulsive, density dependent, two-body potential with a coupling constant C ρ . This force, introduced to simulate a three-body contact force [26], improves the description of bulk properties in closed-shell nuclei [27] and yields more realistic single-particle spectra and multipole-nuclear responses [19,20]. We performed a HFB calculation in a configuration space which includes 13 harmonic oscillator major shells, up to the principal quantum number N max = 12.…”

“…We have first adopted a V lowk potential derived from the CD-Bonn NN interaction to generate a HartreeFock-Bogoliubov (HFB) basis and, then, used such a basis to solve the eigenvalue equations in both (quasi-particle) Tamm-Dancoff ((Q)TDA) and random-phase approximations ((Q)RPA). We could therefore perform a systematic study of the dipole response in several chains of neutron rich isotopes [20]. As in [19], however, we found necessary to add a corrective density dependent piece in order to get single-particle spectra sufficiently compressed so as to reproduce the main peak of the experimental GDR.…”

Mean Field and Beyond Mean Field Calculations of Λ Hypernuclei

“…We intend to mimic the effect of three-body interactions by adding a density-dependent two-body term in the same manner as in ref. [3]. In longer perspective we intend to implement directly the chiral NNN forces into our Hamiltonian.…”

“…All these variants are phenomenological from the point of view that they start from purely effective interactions with no connection to realistic NN forces which reproduce NN scattering data. There are only few works which try to build the nuclear mean-field directly from realistic NN forces [2,3].…”