Peculiarities in the interaction of 6He with 197Au and 206Pb at energies close to the Coulomb barrier

Abstract

Excitation functions for evaporation residues in the reactions 197Au(6He, xn)203-xnTl, where x = 2 - 7, and 206Pb(6He, 2n)210Po, as well as for neutron transfer reactions for the production of 196Au and 198Au in the interaction of 6He with 197Au were measured. 6He beam was obtained from the accelerator complex for radioactive beams DRIBs (JINR). The energy of the incident beam was about 10 MeV/A and the intensity reached 2 ⋅ 107 pps. The stacked foil technique was used directly in the beam extracted from the cyclotron or in the focal plane of the magnetic spectrometer MSP-144. The identification of the reaction products was done by their radioactive γ- or α-decay. Unusually large cross section was observed below the Coulomb barrier for the production of 198Au in the interaction of 6He with 197Au. Possible mechanisms of formation and decay of transfer reaction products are discussed. An increase in the cross section was observed for the fusion reaction with the evaporation of two neutrons compared to statistical model calculations. The analysis of the data in the framework of the statistical model for the decay of excited nuclei, which took into account the sequential fusion of 6He has shown good agreement between the experimental and the calculated values of the cross sections for the case of sub-Coulomb-barrier fusion in the 206Pb + 6He reaction.