Differences Between a Single- and a Double-Folding Nucleus- $$^\mathbf{9}$$ 9 Be Optical Potential

Abstract

We have recently constructed two very successful n-9 Be optical potentials (Bonaccorso and Charity in Phys Rev C89:024619, 2014). One by the Dispersive Optical Model (DOM) method and the other (AB) fully phenomenological. The two potentials have strong surface terms in common for both the real and the imaginary parts. This feature makes them particularly suitable to build a single-folded (light-) nucleus-9 Be optical potential by using ab-initio projectile densities such as those obtained with the VMC method (Wiringa http://www.phy. anl.gov/theory/research/density/). On the other hand, a VMC density together with experimental nucleonnucleon cross-sections can be used also to obtain a neutron and/or proton-9 Be imaginary folding potential. We will use here an ab-initio VMC density (Wiringa http://www.phy.anl.gov/theory/research/density/) to obtain both a n-9 Be single-folded potential and a nucleus-nucleus double-folded potential. In this work we report on the cases of 8 B, 8 Li and 8 C projectiles. Our approach could be the basis for a systematic study of optical potentials for light exotic nuclei scattering on such light targets. Some of the projectiles studied are cores of other exotic nuclei for which neutron knockout has been used to extract spectroscopic information. For those cases, our study will serve to make a quantitative assessment of the core-target part of the reaction description, in particular its localization.

Imaginary part of theC9−Be9single-folded optical potential

“…By comparing to experimental reaction cross sections, we showed in Ref. [2], that for the cases of 8 B, 8 Li and 8 C projectiles, a very good agreement between theory and data could be obtained by adding, at the lower energies, a small surface term to the single-folded potential. In this paper we extend the study to the case of 9 C projectiles, compare to results obtained with the JLM potential [6][7][8][9] and assess the sensitivity of the result to the projectile density used.…”

“…In this section we discuss the details of the 9 C -9 Be imaginary potentials. As already argued in [2], one characteristic of a double-folded potential with a zero-range interaction is that its radial shape is determined solely by those of the densities used. As such the distinction of surface and volume terms cannot be usually reproduced.…”

“…n- 9 Be imaginary potential In Ref. [2] we compared the DOM and AB potentials with the potential from Eq.(6). It was shown that both of these "phenomenological" potentials are shallower in the interior than at the surface, thus having a longer range than the folded potential, although the latter was obtained from a realistic VMC density [4; 5].…”

“…Both calculations reproduce the energy slope and the absolute values of the data. We report for completeness also the experimental values [33; 34] and theoretical cross sections [2] for 8 Li and 8 B projectiles. Note the very close similarity between the 8 B and 9 C values.…”

“…Recently [2] we have argued that using two very successful n- 9 Be optical potentials [3] and microscopic projectile densities, such as the ab-initio VMC [4; 5], it is possible to build a single-folded (light-) nucleus- 9 Be optical potential which is more accurate than a doublefolded optical potential thus overcoming the difficulties discussed above. This is because the n- 9 Be optical potentials have strong surface terms in common for both the real and the imaginary parts which represent deformation effects, giant resonance excitations and the breakup channels of the target.…”