Phase shift analysis of the 6He+208Pb and the 6He+197Au systems (original) (raw)

Long range absorption in the scattering of 6He on 208Pb and 197Au at 27 MeV

Nuclear Physics A, 2006

Quasi-elastic scattering of 6 He at E lab =27 MeV from 197 Au has been measured in the angular range of 6 • − 72 • in the laboratory system employing LEDA and LAMP detection systems. These data, along previously analysed data of 6 He + 208 Pb at the same energy, are analysed using Optical Model calculations. The role of Coulomb dipole polarizability has been investigated. Large imaginary diffuseness parameters are required to fit the data. This result is an evidence for long range absorption mechanisms in 6 He induced reactions.

Study of the elastic scattering of 6He on 208Pb at energies around the Coulomb barrier

Nuclear Physics A, 2008

The elastic scattering of 6 He on 208 Pb has been measured at laboratory energies of 14, 16, 18 and 22 MeV. These data were analyzed using phenomenological Woods-Saxon form factors and optical model calculations. A semiclassical polarization potential was used to study the effect of the Coulomb dipole polarizability. Evidence for long range absorption, partially arising from Coulomb dipole polarizability, is reported. The energy variation of the optical potential was found to be consistent with the dispersion relations which connect the real and imaginary parts of the potential.

Breakup and neutron-transfer effects on ^{6}He+^{206}Pb elastic scattering below the Coulomb barrier

Physical Review C, 2013

The elastic scattering and inclusive α-particle yield for the 6 He + 206 Pb system at an incident energy of 18 MeV, just below the nominal Coulomb barrier, have been measured. The α-particle yield at forward angles is also reported. The data are analyzed by means of continuum-discretized coupled-channels, distorted wave Born approximation, and coupled reaction channels calculations. Couplings to the one-neutron-and two-neutron-transfer reactions are found to be able to account for most of the absorption in the entrance channel.

Elastic scattering for the B8 and Be7+Pb208 systems at near-Coulomb barrier energies

Physical Review C

The elastic scattering of the weakly bound radioactive nuclei 8 B and 7 Be from a 208 Pb target was measured for the first time in the energy range around the Coulomb barrier. The data were analyzed using the optical model and the continuum discretized coupled channels (CDCC) formalisms. The reaction cross sections extracted from the optical model fits clearly indicate a remarkably enhanced reaction probability for the very weakly bound 8 B (S p = 137.5 keV) compared to similar mass nuclei interacting with the same target nucleus. CDCC calculations assuming a 3 He + 4 He cluster model well described the 7 Be experimental elastic scattering angular distributions, whereas the use of a 7 Be + p cluster model of 8 B with an inert 7 Be core gave a relatively poor description of the corresponding experimental data, suggesting that this model may be too simplistic and the possibility of core excitation should not be ignored.

Elastic scattering and transfer in the 6He+209Bi system below the Coulomb barrier

Physical Review C, 2001

The interaction of 6 He with 209 Bi has been studied over a range of energies well below the nominal Coulomb barrier. A 4 He group of remarkable intensity, first observed in a previous experiment at near-barrier energies, continues to dominate the reaction in the sub-barrier regime. A total cross section of nearly 200 mb was measured for this group at 5 MeV below the barrier. This very large value is shown to be consistent with the total reaction cross section deduced from a simultaneouslymeasured elastic scattering angular distribution.

7Be,8B+208Pb Elastic Scattering at Above-Barrier Energies

Journal of Physics: Conference Series, 2013

Angular distributions for the elastic scattering of 7 Be and 8 B by an enriched 208 Pb target were measured at the Radioactive Ion Beam Line at Lanzhou (RIBLL). The incident energies of the radioactive beams were about three times the respective Coulomb barriers. A suppressed Coulomb-nuclear Interference Peak (CNIP) is not observed for 8 B, a pronounced proton halo nucleus. Optical model fits were performed using Woods-Saxon potentials and the total reaction cross sections deduced. The results are discussed.

Four-body effects on9Be+208Pb scattering and fusion around the Coulomb barrier

Journal of Physics: Conference Series, 2015

We investigate the 9 Be+ 208 Pb elastic scattering and fusion at energies around the Coulomb barrier. The 9 Be nucleus is described in a α + α + n three-body model, using the hyperspherical coordinate method. The scattering with 208 Pb is then studied with the Continuum Discretized Coupled Channel (CDCC) method, where the α + α + n continuum is approximated by a discrete number of pseudostates. Optical potentials for the α+ 208 Pb and n+ 208 Pb systems are taken from the literature. We present elastic-scattering and fusion cross sections at different energies, and investigate the convergence with respect to the truncation of the α + α + n continuum. A good agreement with experiment is obtained, considering that there is no parameter fitting. We show that continuum effects increase at low energies.

Comparison of the energy dependence of near-barrier He6 and He8+Pb208 optical potentials

Physical Review C, 2019

Optical model analyses of recent 8 He + 208 Pb elastic scattering data for incident energies of 16 and 22 MeV, together with existing data for 6 He + 208 Pb at the same energies, reveal a significant difference in the behavior of the imaginary part of the optical potential for the two isotopes as the incident energy is reduced below the Coulomb barrier. While the strength of the 6 He imaginary potential reduces as the incident energy is reduced below the barrier, as is the case for most heavy ions, that for 8 He remains constant within uncertainties and may even increase. Similar behavior was observed for the 6 Li and 7 Li + 208 Pb optical potentials [Nucl. Phys. A 571, 326 (1994)], with the strength of the 6 Li imaginary potential appearing to increase as the incident energy is reduced below the Coulomb barrier while that for 7 Li reduces. However, the explanation for this difference in behavior put forward in that work, viz. the increased importance of breakup for 6 Li as the incident energy is reduced towards the Coulomb barrier, later supported explicitly by calculations [Phys. Lett. B 427, 1 (1998)], does not hold for the He isotopes since it is the 8 He optical potential that behaves in a similar fashion to that of 6 Li in spite of 8 He having the higher breakup threshold of the two He isotopes. We conclude that the difference is due to the influence of 3n and 4n stripping on the 8 He scattering, reactions which cannot take place for 6 He projectiles.