Gamma Radiation from the Inelastic Scattering of Protons by F19

The absolute cross section for the excitation of the 109-kev and 197-kev excited states of F19, by the inelastic scattering of protons, has been studied as a function of bombarding energy up to 1750 kev by detecting the resultant gamma radiation in scintillation counters. Most of the resonances for the various F19(p, α)O16 reactions appear as resonances for the excitation of one or both of these low-lying states. A detailed study of the angular distributions of the two gamma rays, together with the direct measurements of the lifetimes of these states by Thirion, Barnes, and Lauritsen, and the Coulomb excitation work of Sherr, Li, and Christy, leads to the assignments: 109-kev state, J=1 / 2, odd parity; 197-kev state, J=5 / 2, even parity. The nonresonant yield of 197-kev gamma rays is approximately that expected from Coulomb excitation at low incident proton energies. The nonresonant yield of 109-kev gamma rays exceeds the expected Coulomb excitation. In conjunction with the recent measurements of the elastic scattering of protons by F19 made by Peterson, Webb, Hagedorn, and Fowler, in this laboratory, and older measurements of the F19(p, α)O16 reactions, the resonant inelastic cross sections allow a new determination of the partial widths for the various modes of decay of the Ne20 compound nuclear states