TheLi8(d,p)Li9reaction and the astrophysicalLi8(n,γ)Li9reaction rate

Abstract

The $^{8}\mathrm{Li}(n,\ensuremath{\gamma})^{9}\mathrm{Li}$ reaction plays an important role in both the r-process nucleosynthesis and the inhomogeneous big bang models. Its direct capture rates can be extracted from the $^{8}\mathrm{Li}(d,p)^{9}\mathrm{Li}$ reaction, indirectly. We have measured the angular distribution of the $^{8}\mathrm{Li}(d,p)^{9}\mathrm{Li}{}_{g.s.}$ reaction at ${E}_{c.m.} = 7.8$ in inverse kinematics using coincidence detection of $^{9}\mathrm{Li}$ and the recoil proton, for the first time. Based on distorted wave Born approximation (DWBA) analysis, the $^{8}\mathrm{Li}(d,p)^{9}\mathrm{Li}{}_{g.s.}$ cross section was determined to be 7.9 \ifmmode\pm\else\textpm\fi{} 2.0 mb. The single particle spectroscopic factor ${S}_{1,3/2}$ for the ground state of $^{9}\mathrm{Li}=^{8}\mathrm{Li}\ensuremath{\bigotimes}n$ was derived to be $0.68\ifmmode\pm\else\textpm\fi{}0.14$, and then used to calculate the direct capture cross sections for the $^{8}\mathrm{Li}(n,\ensuremath{\gamma})^{9}\mathrm{Li}{}_{g.s.}$ reaction at energies of astrophysical interest. The astrophysical $^{8}\mathrm{Li}(n,\ensuremath{\gamma})^{9}\mathrm{Li}{}_{g.s.}$ reaction rate for the direct capture was found to be $3970\ifmmode\pm\else\textpm\fi{}950\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{3}\phantom{\rule{0.3em}{0ex}}{\mathrm{mole}}^{\ensuremath{-}1}\phantom{\rule{0.3em}{0ex}}{s}^{\ensuremath{-}1}$ at ${T}_{9}=1.$ This presents the first experimental constraint for the $^{8}\mathrm{Li}(n,\ensuremath{\gamma})^{9}\mathrm{Li}$ reaction rates of astrophysical relevance.