Lifetimes of the First Four Excited States inSi29

The attenuated-Doppler-shift method was used to measure the lifetimes of the first four excited states in ${\mathrm{Si}}^{29}$. The states were populated by the ${\mathrm{Si}}^{28}\mathrm{}(d,p)\mathrm{}$ reaction and the direction of a recoil was defined by the direction of the outgoing proton with which it was in coincidence. The shifts were measured both for the stopping of recoils in a heavy material (gold) and for stopping in a light material (silicon or carbon). The lifetimes of these excited states were found to be $3.1_{-0.8\mathrm{}}^{}{}_{}{}^{+1.1\mathrm{}}$×${10}^{-13\mathrm{}}$ sec for the first, 3$.5_{-0.8\mathrm{}}^{}{}_{}{}^{+0.9\mathrm{}}$×${10}^{-13\mathrm{}}$ sec for the second, (2.0±0.7)×${10}^{-14\mathrm{}}$ sec for the third, and (2.3±1.1)×${10}^{-14\mathrm{}}$ sec for the fourth. It is concluded that no simple picture adequately describes the low-lying states in ${\mathrm{Si}}^{29}$, but that a mixture of two rotational bands shows promise.