Scattering of He3 by He4 and of He4 by tritium

Abstract

The differential elastic scattering cross section has been measured for the scattering of He3 from He4 and the scattering of He4 from tritium for bombarding energies of 5 to 18 and 4 to 18 MeV, respectively. Data were also obtained for the reactions He4(He3,p)Li6, He4(He3,p′)Li6*, H3(α,n)Li6, and H3(α,n′)Li6*. Levels are seen at 4.65, 6.64, 7.47, and 9.7 MeV in Li7, and at 4.57, 6.73, 7.21, and 9.3 MeV in Be7. A phase-shift analysis suggests assignments of 7/2- and 5/2- for the two lower levels in Li7, confirms the 5/2- assignment of the 7.47 level, and suggests a 7/2- assignment for the new level at 9.7 MeV. Similarly in Be7, the assignments of 7/2- and 5/2- for the lower two levels are confirmed, and an assignment of 7/2- is suggested for the new level at 9.3 MeV. The reduced widths for α 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.