New analysis method of the halo phenomenon in finite many-fermion systems: First applications to medium-mass atomic nuclei

Abstract

A new analysis method to investigate halos in finite many-fermion systems is designed, as existing characterization methods are proven to be incomplete/inaccurate. A decomposition of the internal wave-function of the N -body system in terms of overlap functions allows a model-independent analysis of medium-range and asymptotic properties of the internal one-body density. The existence of a spatially decorrelated region in the density profile is related to the existence of three typical energy scales in the excitation spectrum of the (N −1)-body system. A series of model-independent measures, taking the internal density as the only input, are introduced. The new measures allow a quantification of the potential halo in terms of the average number of fermions participating to it and of its impact on the system extension. Those new "halo factors" are validated through simulations and applied to results obtained through energy density functional calculations of medium-mass nuclei. Performing spherical Hartree-Fock-Bogoliubov calculations with state-of-the-art Skyrme plus pairing functionals, a collective halo is predicted in drip-line Cr isotopes, whereas no such effect is seen in Sn isotopes.

Evolution of surface deformations of weakly bound nuclei in the continuum

“…Extensive studies have been done to look for deformed halo structures in light nuclei experimentally [11,20,21] and theoretically [8,[22][23][24]. For halos in weakly bound heavy nuclei, theoretical studies are mostly done with spherical nuclear shapes [25][26][27][28][29]. The studies of deformed heavy halos based on self-consistent HFB calculations are still absent.…”

Pairing correlations and odd-even staggering in reaction cross sections of weakly bound nuclei

“…This is referred to as the antihalo effect due to the pairing correlations [5,6,12]. It was shown in Ref.…”

“…The halo structure is one of the characteristic features of weakly bound nuclei and has attracted lots of attention (see Refs. [5] and [6] for detailed theoretical studies on the halo phenomena and Ref. [7] for a recent discovery of the halo structure in 31 Ne nucleus).…”

“…That is, the OES in reaction cross sections is intimately related to the so-called pairing antihalo effect discussed in Refs. [5], [6], and [12]. On the other hand, there have been contradictory arguments about whether the pairing gap disappears [13] or persists [6,14,15] when a nucleus reaches at the neutron drip line, that is, when the single-particle energy of the last occupied orbit approaches the zero energy.…”

The coordinate-space Hartree-Fock-Bogoliubov approach for describing weakly-bound deformed nuclei

“…Extensive studies have been done to look for deformed halo structures in light nuclei experimentally [27,28] and theoretically [10,[29][30]. In weakly-bound heavy nuclei, theoretical studies are mostly done with spherical shape and are model dependent [31][32][33][34][35]. In this context, we systematically studied the even-even weakly-bound deformed nuclei from light to heavy mass region based on the self-consistent coordinate-space Skyrme HFB approach.…”