Abstract
Using the Livermore variable-energy cyclotron time-of-flight facility, the angular distribution of the neutrons from the () reaction on , , and has been measured in 15° steps from 0° to 135° for 13 proton energies between 7 and 13.5 MeV. The persistence of a rather large ground-state reaction () over the entire energy region studied clearly indicates the operation of a spin-flip mechanism in the effective two-body force. The and isobaric cross sections () are experimentally observed to be roughly equal, while optical-model calculations (including the isospin potential) predict cross sections to be twice as large as those for . This disagreement can be qualitatively explained by the presence of a large spin-flip term in the effective two-body force. The and the cross sections indicate a sizeable value for the quadrupole term in the multipole expansion of the effective two-body force. These data and other light-nucleus data are analyzed using the distorted-wave Born approximation to yield an estimate of the effective central two-body interaction. For an assumed Yukawa force with a range of 1.4 fm, this analysis yields MeV and MeV. A comparison is made between these force constants and those obtained from other sources.
- Received 8 August 1968
DOI:https://doi.org/10.1103/PhysRev.177.1416
©1969 American Physical Society