Scattering of Alpha Particles by Oxygen. I. Bombarding Energy Range 5.8 to 10.0 MeV

Abstract

Absolute differential cross sections for the elastic scattering of $\alpha$ particles by ${\mathrm{O}}^{16}$ have been measured as a function of bombarding energy in the range 5.8-10.0 MeV. Measurements were made at center-of-mass angles of 90.0°, 109.9°, 114.0°, 125.3°, 131.4°, 140.8°, 149.4°, 154.0°, 158.8°, and 163.8°. Detailed angular distributions have been measured at 6.97, 8.63, and 9.92 MeV (lab). Sixteen resonances have been observed corresponding to energy levels in ${\mathrm{Ne}}^{20}$ at 9.50, 9.99, 10.30, 10.49, 10.55, ∼10.7, 10.83, (10.93), 11.03, 11.29, ∼11.6, (11.89), 11.99, 12.27, 12.39, and 12.58 MeV (c.m.). Spin and parity assignments have been made for six of these levels, tentative assignments are suggested for seven, and two or more possible assignments are given for two levels. Phase shifts have been extracted from the angular distribution data at 6.97, 8.63, and 9.92 MeV (lab). New rotational bands in ${\mathrm{Ne}}^{20}$ are suggested by the data and previously reported bands have been extended. Information about the levels in ${\mathrm{Ne}}^{20}$ is compared with that obtained in previous studies of other nuclear reactions. The correspondence with the results of an ${\mathrm{O}}^{16}(\alpha , \gamma ){\mathrm{Ne}}^{20}$ investigation is generally good. The set of ${\mathrm{Ne}}^{20}$ levels found in this work is somewhat different from the set determined by the ${\mathrm{C}}^{12}({\mathrm{C}}^{12}, \alpha ){\mathrm{Ne}}^{20}$ reaction experiments, and this difference is discussed.