A search for continuum levels in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ with a large ${[}^{16}$O($0_2^{+}$)+α] parentage has been conducted using both resonant and direct production processes. The differential cross section for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(α,${\mathrm{\alpha }}_1$${)}^{16}$${\mathrm{O}}^{\mathrm{*}}$($0_2^{+}$) reaction has been measured at 13 to 26 angles for bombarding energies from ${\mathit{E}}_{\mathrm{\alpha }}$=10.2 to 18 MeV, mostly in 25 keV steps. Events leading to the first excited state in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ were identified by requiring the coincident observation of an α particle and an electron or positron from the internal pair decay of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ first excited state. Amplitudes of individual partial waves were extracted from the data by parametrizing the angular distributions in terms of the complex zeros of the scattering amplitudes. An R-matrix analysis of the data reveals a ${\mathit{J}}^{\mathrm{\pi }}$=$2^{+}$ level at ${\mathit{E}}_{\mathit{x}}$=13.1 MeV with a spectroscopic factor ${\mathrm{\Theta }}_{\mathrm{\alpha }1}^2$>63%.

Several individual levels, a region of overlapping ${\mathit{J}}^{\mathrm{\pi }}$=$4^{+}$ levels from ${\mathit{E}}_{\mathit{x}}$=13.69 to 14.93 MeV and a region of ${\mathit{J}}^{\mathrm{\pi }}$=$6^{+}$ levels from ${\mathit{E}}_{\mathit{x}}$=16.73 to 18.73 MeV, have also been analyzed in detail. Branching ratios of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ levels to the first excited state in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been measured by populating the levels with the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${(}^{12}$C,α${)}^{20}$${\mathrm{Ne}}^{\mathrm{*}}$ and observing their subsequent α decay to the $0_2^{+}$ state of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. A ${\mathit{J}}^{\mathrm{\pi }}$=$6^{+}$ level at ${\mathit{E}}_{\mathit{x}}$=15.16 MeV and a ${\mathit{J}}^{\mathrm{\pi }}$=$8^{+}$ level at ${\mathit{E}}_{\mathit{x}}$=18.54 MeV, which had previously been suggested as members of a rotational band based on the ${\mathit{J}}^{\mathrm{\pi }}$=$0^{+}$ level in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ at ${\mathit{E}}_{\mathit{x}}$=12.44 MeV are shown to have small values of ${\mathrm{\Theta }}_{\mathrm{\alpha }1}^2$, arguing against this identification.

• Received 23 September 1991

DOI:https://doi.org/10.1103/PhysRevC.45.576