A formalism for the analysis of Doppler-broadened $\gamma$-ray line shapes observed in ($a, b\gamma$) reactions, has been developed in order to measure nuclear lifetimes. The technique, which is generally applicable to lifetime determinations in the range 5×${10}^{-15\mathrm{}}$ to ${10}^{-13\mathrm{}}$ sec, has been employed to measure the lifetimes of the levels at 4.43 MeV in ${\mathrm{C}}^{12}$ and 6.92 MeV in ${\mathrm{O}}^{16}$. Results of 65±9 and ${6.4}_{-1.6\mathrm{}}^{+1.9\mathrm{}}$ fsec, respectively, were obtained.

• Received 7 November 1969

DOI:https://doi.org/10.1103/PhysRevC.1.1757