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 ${\theta }_{\mathrm{lab}}=18\mathrm{}° \mathrm{and} 85°$. 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. $B\left(E2\mathrm{}\right)\mathrm{}\downarrow$ 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±3 and 10±3 W.u. (single-particle units). They were calculated from the ${\beta }_2$ 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 $B\left(E3\mathrm{}\right)\mathrm{}\downarrow$ value for the ${\frac{5}{2}}^{-}\to {\frac{1}{2}}^{+}$ transition from the 1.35-MeV state was found to be 1.4±0.6 W.u. as compared to the upper limit of 3.8±0.6 W.u. from a ($p, p^{\prime }$) experiment, and to 12.0±4.0 and 7.6±1.3 W.u. from two different Coulomb-excitation experiments. The results are compared to various model predictions.