Microscopic description of spin distributions in multinucleon tranfer reactions

Abstract

Background: The generation of spin distributions in fission fragments has attracted substantial interest in recent years and its mechanism is becoming clear alongside the refined description with microscopic theories. In contrast, the microscopic origin of spin distributions in reaction products remain largely unexplored. Methods: Three-dimensional TDHF calculations are performed for multinucleon transfer processes in the ${}^{40}\text{Ca}+{}^{124}\text{Sn}$ reaction at $E_{\text{c.m.}}\simeq 128.54\text{MeV}$ using the Skyrme SLy5 energy density functional. To obtain spin distributions in each transfer channel, the particle-number projection (PNP) and the angular-momentum projection (AMP) are simultaneously achieved for a reaction product. Results: By performing PNP+AMP for TDHF wave functions after collisions, spin-dependent transfer cross sections are calculated for projectile-like fragments (PLFs). From the results, we find that abundant spin distributions can be obtained from the TDHF wave functions. For one-nucleon addition and removal channels, the calculated spin values agree well with those of single-particle states in the $pf$- and $sd$-shell, respectively. Moreover, for a-few-nucleon transfer channels, we show that the obtained spin distributions can be well explained by combinations of total angular momenta of those single-particle states. Furthermore, as the number of transferred nucleons increases, we find that the calculated spin distributions exhibit a smooth singly-peaked shape with a long tail as a function of $J$, which resembles that of empirical spin distributions for thermally equilibrated fragments. An exploratory calculation for induced fission of ${}^{240}$Pu is also carried out, obtaining similar results as in multinucleon transfer reactions. (shorted due to the arXiv's word limit)

Comments: 18 pages, 12 figures