Multipole deformations in 19F and in the neon isotopes and electric multipole strength in 19F from inelastic scattering of 30 MeV protons

Cross sections were measured for inelastic scattering of 30 MeV protons from 19 F, 20 Ne, 21 Ne, and 22 Ne. The cross sections of the ground state rotational band in these nuclei were analyzed in the coupled channels formalism and yield further evidence for a large hexadecapole deformation in 19 F (β 4 = 0.14 ± 0.04) and in 20 Ne (β 4 = 0.28 ± 0.05) in good agreement with several recent proton inelastic scattering experiments. These calculations show also that the Y 4 moment is small or close to zero in 21 Ne and 22 Ne (β 4 ≤ 0.05). The analysis of the available 19 F cross section in the DWBA formalism shows evidence for a large and significant octupole transition strength for the 1.35 MeV (5/2 − ) (3.6 W.u.), the 5.43 MeV (7/2 − ) state (6.70 W.u.), and the 5.63 MeV (5/2 − ) state (3.60 W.u.). The measured transition strengths are generally in disagreement with recent low energy (α, α′) or (d, d′) results but also with the earlier Coulomb excitation measurements. Thus, we confirm that a major discrepancy still exists between inelastic scattering and Coulomb excitation of the octupole transition strength to several states in 19 F but mainly to the 1.35 MeV (5/2 − ) state as was already pointed out some time ago from a low energy inelastic proton scattering experiment. On a mesuré les sections efficaces pour la diffusion inélastique de protons de 30 MeV excitant les noyaux 19 F, 20 Ne, 21 Ne et 22 Ne.