Comprehensive analysis of high-lying states in O18 populated with (t,p) and (O18,O16) reactions

Abstract

Background: In our recent work [M. J. Ermamatov et al., Phys. Rev. C 94, 024610 (2016)], the two-neutron transfer induced by the $(^{18}\mathrm{O},^{16}\mathrm{O})$ reaction was studied for $^{16}\mathrm{O}$ nucleus. Theoretical analysis of the low-lying states of $^{18}\mathrm{O}$ indicates that the transfer to the ground state proceeds predominantly through simultaneous transfer of the two-neutron system.Purpose: In this work, we extend our previous theoretical analysis towards high-lying states of the $^{18}\mathrm{O}$ nucleus. In order to achieve a comprehensive picture, we revisit the experimental data for the $^{16}\mathrm{O}(t,p)^{18}\mathrm{O}$ reaction at 15 MeV bombarding energy. We also include new experimental cross sections for the high-lying states of the $^{18}\mathrm{O}$ residual nucleus, populated in the $^{16}\mathrm{O}(^{18}\mathrm{O},^{16}\mathrm{O})^{18}\mathrm{O}$ reaction at 84 MeV.Method: The same spectroscopic parameters of the target nucleus were used as input in the coupled channel calculations for the transfer induced by triton and $^{18}\mathrm{O}$ projectiles. Simultaneous two-neutron transfer is calculated within the coupled reaction channel approach, using the extreme cluster and independent coordinate models. The sequential process is calculated within the distorted-wave Born approximation.Results: Theoretical calculations reproduce the $^{16}\mathrm{O}(t,p)^{18}\mathrm{O}$ data well, leading to natural parity states in the $^{18}\mathrm{O}$ nucleus without the need of adjustable parameters. The same methods are applied to the $^{16}\mathrm{O}(^{18}\mathrm{O},^{16}\mathrm{O})^{18}\mathrm{O}$ data and a good agreement is observed.Conclusions: Detailed analyses show the importance of a simultaneous mechanism for the two-neutron transfer reactions. In transferring two neutrons, the pairing correlation plays an important role.