Multi-neutron transfer in ${}^8$He induced reactions near the Coulomb barrier

Abstract

The measured inclusive ${}^6$He and ${}^4$He production cross sections of G. Marquínez-Durán {\em et al.}, Phys.\ Rev.\ C {\bf 98}, 034615 (2018) are reexamined and the conclusions concerning the relative importance of 1n and 2n transfer to the production of ${}^6$He arising from the interaction of a 22 MeV ${}^8$He beam with a ${}^{208}$Pb target revised. A consideration of the kinematics of the 2n-stripping reaction when compared with the measured ${}^6$He total energy versus angle spectrum places strict limits on the allowed excitation energy of the ${}^{210}$Pb residual, so constraining distorted wave Born approximation calculations that the contribution of the 2n stripping process to the inclusive ${}^6$He production can only be relatively small. It is therefore concluded that the dominant ${}^6$He production mechanism must be 1n stripping followed by decay of the ${}^7$He ejectile. Based on this result we present strong arguments in favor of direct, one step four-neutron (4n) stripping as the main mechanism for ${}^4$He production.

Comments: 7 pages, 2 figures