Octupole and Quadrupole Transition Rates inF19from Scattering of 15-MeV Deuterons

Abstract

Angular distributions of 15.0-MeV deuterons scattered by ${\mathrm{F}}^{19}$ were measured between ${\ensuremath{\theta}}_{\mathrm{lab}}=18\ifmmode^\circ\else\textdegree\fi{} \mathrm{and} 85\ifmmode^\circ\else\textdegree\fi{}$. Inelastic groups leaving ${\mathrm{F}}^{19}$ in its five lowest-lying excited states were observed using two position-sensitive detectors placed in the focal plane of a split-pole spectrometer. The elastic-scattering cross section was analyzed using an optical model. $B(E2)\ensuremath{\downarrow}$ values for the transitions from the $\frac{5}{2}$+(0.197-MeV) and the $\frac{3}{2}$+(1.56-MeV) states to the ground state were found to be 9\ifmmode\pm\else\textpm\fi{}3 and 10\ifmmode\pm\else\textpm\fi{}3 W.u. (single-particle units). They were calculated from the ${\ensuremath{\beta}}_{2}$ deformation parameter extracted from a distorted-wave Born-approximation (DWBA) analysis using a complex form factor derived from the optical-model analysis with a surface-absorption term. These results are in good agreement with results obtained from inelastic proton scattering and from Coulomb-excitation experiments. However, the $B(E3)\ensuremath{\downarrow}$ value for the ${\frac{5}{2}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\frac{1}{2}}^{+}$ transition from the 1.35-MeV state was found to be 1.4\ifmmode\pm\else\textpm\fi{}0.6 W.u. as compared to the upper limit of 3.8\ifmmode\pm\else\textpm\fi{}0.6 W.u. from a ($p, {p}^{\ensuremath{'}}$) experiment, and to 12.0\ifmmode\pm\else\textpm\fi{}4.0 and 7.6\ifmmode\pm\else\textpm\fi{}1.3 W.u. from two different Coulomb-excitation experiments. The results are compared to various model predictions.