Multiconfiguration resonating-group theory ofLi8

The nucleus ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$ is studied with a multiconfiguration resonating-group calculation which consists of n${+}^7$Li, t${+}^5$He, n${+}^7$ ${\mathrm{Li}}^{\mathrm{*}}$, and ${}_{}{}^4{}_{}{}^{}$H+α cluster configurations. With no adjustable parameters, the results show that the calculated level spectrum agrees well with experiment and with the empirical level spectrum obtained by Knox, Resler, and Lane using an extensive R-matrix analysis. A calculation employing only the n${+}^7$Li configuration is found to be generally inadequate. Among the configurations t${+}^5$He, n${+}^7$ ${\mathrm{Li}}^{\mathrm{*}}$, and ${}_{}{}^4{}_{}{}^{}$H+α which are employed to enlarge the model space, the n${+}^7$ ${\mathrm{Li}}^{\mathrm{*}}$ configuration is shown to be the most important from an overall viewpoint. Comparisons between calculated and experimental scattering and reaction cross sections have also been made. Here one finds that the calculation explains all the main features of measured results. In particular, the triton production cross section of the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(n,n’t)α reaction is well reproduced. The calculated n${+}^7$Li total reaction cross section turns out to be somewhat too small, being equal to around 75% of the experimental value.