Study of the Low-Lying Excited States ofAl29. III. Mean Lifetimes and Interpretation

Lifetimes or, alternatively, limits for lifetimes of low-lying levels in ${}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ have been obtained employing the Doppler-shift-attenuation method. The levels were excited by the ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}\mathrm{}(t,p)\mathrm{}{}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ reaction and measurements were made of the $\gamma$-ray spectrum in coincidence with reaction protons. Measured mean lifetimes, or limits, [$E_x\left({\tau }_m\right)$, in MeV (psec)] for the first six levels of ${}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ are: $1.402\left({3.3}_{-1.0\mathrm{}}^{+2.2\mathrm{}}\right)$, 1.762 (${}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ for excitation energy $E_x<~4.5$ MeV based on previously reported information is presented. Properties of these levels are interpreted according to the Nilsson model on the basis of (1) a direct-reaction investigation and (2) $\gamma$-ray angular-correlation investigations as previously reported. The properties of ${}_{}{}^{29}{}_{}{}^{}\mathrm{Al}$ are shown to be consistent with a prolate deformation characterized by $\eta \approx +3\mathrm{}$.