Scattering of He3 by He4 and of He4 by Tritium

Abstract

The differential elastic scattering cross section has been measured for the scattering of ${\mathrm{He}}^3$ from ${\mathrm{He}}^4$ and the scattering of ${\mathrm{He}}^4$ from tritium for bombarding energies of 5 to 18 and 4 to 18 MeV, respectively. Data were also obtained for the reactions ${\mathrm{He}}^4({\mathrm{He}}^3,p){\mathrm{Li}}^6$, ${\mathrm{He}}^4({\mathrm{He}}^3,p^{\prime }){\mathrm{Li}}^{6*}$, ${\mathrm{H}}^3(\alpha ,n){\mathrm{Li}}^6$, and ${\mathrm{H}}^3(\alpha ,n^{\prime }){\mathrm{Li}}^{6*}$. Levels are seen at 4.65, 6.64, 7.47, and 9.7 MeV in ${\mathrm{Li}}^7$, and at 4.57, 6.73, 7.21, and 9.3 MeV in ${\mathrm{Be}}^7$. A phase-shift analysis suggests assignments of ${\frac{7}{2}}^{-}$ and ${\frac{5}{2}}^{-}$ for the two lower levels in ${\mathrm{Li}}^7$, confirms the ${\frac{5}{2}}^{-}$ assignment of the 7.47 level, and suggests a ${\frac{7}{2}}^{-}$ assignment for the new level at 9.7 MeV. Similarly in ${\mathrm{Be}}^7$, the assignments of ${\frac{7}{2}}^{-}$ and ${\frac{5}{2}}^{-}$ for the lower two levels are confirmed, and an assignment of ${\frac{7}{2}}^{-}$ is suggested for the new level at 9.3 MeV. The reduced widths for $\alpha$ and nucleon emission were determined by fitting the phase shifts near each level with a single- and/or double-level formula from the $R$-matrix formalism of Lane and Thomas. The results of the analysis are discussed and compared with predictions of recent nuclear-model calculations.