Gamma-Ray Angular Correlations and Lifetime Measurements for Some Excited States ofNe21

Excited states of ${\mathrm{Ne}}^{21}$ were studied using the ${\mathrm{O}}^{18}(\alpha , n\gamma ){\mathrm{Ne}}^{21}$ reaction at beam energies of 2.9 to 6.9 MeV. The investigation involved the measurement of $\gamma -\gamma$ and $n-\gamma$ angular correlations to obtain spin and multipole-mixing-ratio assignments for five states in ${\mathrm{Ne}}^{21}$. In addition, a Ge(Li) detector was used to measure the lifetimes of these states by the Doppler-shift-attenuation method. The investigation resulted in the following assignments for the five states: $E_x$ (keV), $J, \tau \left(\mathrm{psec}\right)=3663.5\mathrm{}\pm 2.0, \frac{3}{2}, 0.12\pm 0.02; 3734.8\pm 1.5, \frac{3}{2} or \frac{5}{2}, <0.067; 3885.5\pm 1.5,\frac{3}{2}or\frac{5}{2}, 0.078\pm 0.027;4431.3\pm 2.0, \frac{7}{2} or\frac{11}{2}, 0.078\pm 0.027;\mathrm{and} 4526.1\pm 1.5, \frac{3}{2} or \frac{5}{2}, <0.067\mathrm{}$. Some of the results have been interpreted in terms of the Nilsson model, and a comparison of the excited states of the $\xi =11\mathrm{}$ nuclei has been made.