Doppler shifts of $\gamma$ rays from some excited states of ${\mathrm{B}}^{10}$ nuclei produced in the reaction ${\mathrm{B}}^{11}({\mathrm{He}}^3,\alpha ){\mathrm{B}}^{10}$ have been measured with Ge(Li) and NaI(Tl) detectors. From these Doppler shifts the following information concerning mean lives of states in ${\mathrm{B}}^{10}$ has been deduced: $\tau \left(1.74\mathrm{} \mathrm{MeV}\right)\le 4\times {10}^{-14\mathrm{}}$ sec, $\tau \left(2.15\mathrm{} \mathrm{MeV}\right)=\left(2.1_{-0.5\mathrm{}}^{}{}_{}{}^{+0.8\mathrm{}}\right)\times {10}^{-12\mathrm{}}$ sec, and $\tau \left(3.59\mathrm{} \mathrm{MeV}\right)=(1.7\mathrm{}\pm 0.7)\times {10}^{-13\mathrm{}}$ sec.

• Received 27 July 1967

DOI:https://doi.org/10.1103/PhysRev.165.1071