The optical potential of 6He in the eikonal approximation
Abstract The new data of the elastic scattering of 6 He+ 12 C at about 40 MeV/nucleon are analyzed in the eikonal approximation. The 6 He+ 12 C phase-shift function is evaluated completely without any ad hoc assumption by a Monte Carlo integration, which makes it possible to use a realistic 6-nucleon wave function for a halo nucleus 6 He. The effect of the breakup of 6 He on the elastic differential cross sections as well as the optical potential is studied at different energies from 40 to 800 MeV/nucleon.
Four-body calculation of 6He breakup with the Coulomb-corrected eikonal method
The elastic breakup of a three-body projectile on a target is studied within the eikonal approximation with full account of final-state interactions. Bound and scattering states are calculated in hyperspherical coordinates on a Lagrange mesh. A correction is introduced to avoid the divergence of breakup cross sections due to the Coulomb interaction. The eikonal approximation allows the direct calculation of various cross sections, and in particular multidifferential cross sections can be obtained. The model is applied to the breakup of {sup 6}He on {sup 208}Pb. The {sup 6}He halo nucleus is described within a three-body {alpha}+n+n model involving effective {alpha}n and nn interactions. The eikonal phase is obtained from optical potentials between {alpha} and n, and the target. Around 0.8 MeV, the total breakup cross sections exhibit a narrow 2{sup +} resonant peak superimposed over a broad bump corresponding to a 1{sup -} resonance. These results suffer from a disagreement with experimental data at 240 MeV/nucleon, where cross sections are much smaller at low energies. The obtained E1 strength distribution resembles other theoretical results and reopens a long-standing problem about the existence of a 1{sup -} low-energy resonance in the {sup 6}He continuum.
Anomalous Annealing Behavior of Arsenic Implanted Silicon as a Function of Dose and Energy
Anomalous annealing behavior of damage in As implanted Si has been investigated by channeling effect measurements. Room temperature As implants with doses from 1014 to 2 × 1016cm-2 at energies ranging from 50 to 250 keV into Si were annealed over the range of 600°C to 1100°C. Anneal temperatures ≥ 950°C reduce the disorder for ion doses of 0.5 to 1 × 1016 cm-2 at energies between 50 and 250 keV. Anomalously high residual disorder was found for the intermediate doses of 2 × 1014 to 2 × 10/cm2 implanted above 100 keV. For this intermediate dose, annealing of implants performed at liquid nitrogen temperatures did not show significant reduction in this damage. However implants at 200° to 300°C indicate a lower amount of damage compared to the room temperature implants.