Influence of single-neutron stripping on near-barrier He6+Pb208 and He

Abstract

The influence of single-neutron stripping on the near-barrier elastic scattering angular distributions for the 6,8 He + 208 Pb systems is investigated through coupled reaction channels (CRC) calculations fitting recently published data to explore the differences in the absorptive potential found in the scattering of these two neutronrich nuclei. The inclusion of the coupling reduces the elastic cross section in the Coulomb-nuclear interference region for 8 He scattering, whereas for 6 He its major impact is on the large-angle elastic scattering. The real and imaginary dynamic polarization potentials are obtained by inverting the CRC elastic scattering S-matrix elements. These show that the main absorptive features occur between 11 and 12 fm for both projectiles, while the attractive features are separated by about 1 fm, with their main structures occurring at 10.5 fm for 6 He and 11.5 fm for 8 He.

Interaction of He8 with Pb208 at near-barrier energies: HeMarquínez-Durán1, Martel2, Sánchez-Benítez3 et al. 2018Phys. Rev. CSelf Cite10020View full textAdd to dashboardCite

“…[1,5]. As shown in these works, the double-sided silicon strip detector E-E telescopes of the GLORIA array [5] provided clear separation between the He isotopes produced in the interaction between the beam and target so that the 8 He, 6 He, and 4 He yields were unambiguously extracted. The strip detectors are subdivided into pixels, defined as the intersection of a p strip (vertical) and an n strip (horizontal), see Ref.…”

“…In addition to the previously reported elastic scattering data at a 8 He incident energy of 22 MeV [1], elastic scattering data were also obtained at 16 MeV and 6 He and 4 He yields at both energies. Figure 1(a) shows the events from all the strip detectors gated on 4 He at 22 MeV.…”

“…Recently, precise data for the elastic scattering of 8 He from a 208 Pb target at an incident energy of 22 MeV, slightly above the Coulomb barrier, were presented and compared with existing data for 6 He + 208 Pb at the same incident energy [1]. A larger total reaction cross section was obtained for 8 He than for 6 He, suggesting an increased neutron stripping cross section for 8 He that more than compensates for an expected lower breakup cross section than 6 He, due to its higher breakup threshold and probable weaker dipole coupling to the continuum.…”

“…Excitation functions are reported which show that neutron stripping dominates over fusion for energies up to about 10 MeV above the barrier. Coupled reaction channels (CRC) calculations that describe the total neutron transfer strength provide a good simultaneous description of the fusion excitation function, suggesting that breakup is not as important for 8 He as for 6 He. A comparison between the fusion cross sections (σ Fus ) for the 4,6,8 He + 197 Au systems showed that σ Fus for 6 He and 8 He are similar at energies below the barrier and larger than for 4 He.…”

“…In this work, we present inclusive 4 He and 6 He production angular distributions for the 8 He + 208 Pb system at incident energies of 16 and 22 MeV. A combination of kinematics and calculations enables a number of conclusions to be drawn concerning the relative importance of neutron stripping reactions, as well as an upper limit on the fusion cross section at 22 MeV.…”