Comprehensive analysis of large α yields observed in Li6 -induced reactions

Abstract

Background: Large α yields have been reported over the years in reactions with 6 Li and 7 Li projectiles. Previous theoretical analyses have shown that the elastic breakup (EBU) mechanism (i.e., projectile breakup leaving the target in its ground state) is able to account only for a small fraction of the total α-inclusive breakup cross sections, pointing toward the dominance of nonelastic breakup (NEB) mechanisms. Purpose: We aim to provide a systematic study of the α-inclusive cross sections observed in nuclear reactions induced by 6 Li projectiles. In addition to estimating the total α singles' cross sections, it is our goal to evaluate angular and energy distributions of these α particles and compare them with experimental data, when available. Method: We compute separately the EBU and NEB components of the inclusive breakup cross sections. For the former, we use the continuum-discretized coupled-channels (CDCC) method, which treats this mechanism to all orders. For the NEB part, we employ the model proposed by Ichimura et al. [Phys. Rev. C 32, 431 (1985)], within the distorted-wave Born approximation (DWBA). Results: Overall, the sum of the computed EBU and NEB cross sections is found to reproduce very well the measured singles' cross sections. In all cases analyzed, we find that the inclusive breakup cross section is largely dominated by the NEB component. Conclusions:The presented method provides a global and systematic description of inclusive breakup reactions induced by 6 Li projectiles. It provides also a natural explanation of the previously observed underestimation of the measured α yields by CDCC calculations. The method used here can be extended to other weakly bound projectiles, including halo nuclei.

Inclusive breakup calculations in angular momentum basis: Application to Li7+Ni58

“…The results presented in this work, along with those presented in previous works [7,8,13], indicate that the IAV model provides a reliable framework to calculate NEB cross sections. Possible applications to knockout reactions at intermediate energies are currently under study.…”

“…Recently , the model model has been re-examined by several groups [7][8][9][10][11][12]. Moreover a systematic study of the alpha productions in 6 Li induced reactions has been recently reported by Lei and Moro [13], in which the numerical calculations using the IAV model agree well with the experimental data.…”

“…Then inserting complete set of states in Eq. (13) and making use of the geometrical coefficients G out←in αin,αout (r x r b x), we arrive at the following equation:…”

Post-prior equivalence for transfer reactions with complex potentials

“…These works have concluded that the UT formula is incomplete, and must be supplemented with additional terms, as we show below. The comparison of the IAV and UT models with experimental data supports this interpretation [12][13][14][15][16][17] In general, the NEB will contain also contributions coming from the population of states below the breakup threshold of the x + A system (E x < 0). One would like to have a common framework to describe transfer to both continuum as well as bound states.…”

Reaction dynamics studies for the system 7Be + 208Pb at Coulomb barrier energies

“…A detailed analysis of the 3,4 He angular distributions and energy spectra will be the subject of a forthcoming investigation, maybe in the framework of the model recently developed by Lei and Moro [36].…”