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

Abstract

Excited states of ${\mathrm{Ne}}^{21}$ were studied using the ${\mathrm{O}}^{18}(\ensuremath{\alpha}, n\ensuremath{\gamma}){\mathrm{Ne}}^{21}$ reaction at beam energies of 2.9 to 6.9 MeV. The investigation involved the measurement of $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ and $n\ensuremath{-}\ensuremath{\gamma}$ 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), $J, \ensuremath{\tau}(\mathrm{psec})=3663.5\ifmmode\pm\else\textpm\fi{}2.0, \frac{3}{2}, 0.12\ifmmode\pm\else\textpm\fi{}0.02; 3734.8\ifmmode\pm\else\textpm\fi{}1.5, \frac{3}{2} or \frac{5}{2}, <0.067; 3885.5\ifmmode\pm\else\textpm\fi{}1.5,\frac{3}{2}or\frac{5}{2}, 0.078\ifmmode\pm\else\textpm\fi{}0.027;4431.3\ifmmode\pm\else\textpm\fi{}2.0, \frac{7}{2} or\frac{11}{2}, 0.078\ifmmode\pm\else\textpm\fi{}0.027;\mathrm{and} 4526.1\ifmmode\pm\else\textpm\fi{}1.5, \frac{3}{2} or \frac{5}{2}, <0.067$. Some of the results have been interpreted in terms of the Nilsson model, and a comparison of the excited states of the $\ensuremath{\xi}=11$ nuclei has been made.