The Doppler-shift method is used to obtain lifetime limits of $\tau <10\mathrm{}$ fsec and $\tau <26\mathrm{}$ fsec for the 3.09- and 3.68-MeV levels of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, respectively. The radiative width ${\Gamma }_{\gamma }$ is remeasured for the 2.37-MeV state of ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$ in the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(p, \gamma ){}_{}{}^{13}{}_{}{}^{}\mathrm{N}$ and found to be 0.45±0.05 eV, corresponding to $\tau =1.47\mathrm{}\pm 0.15$ fsec. Thus, the disagreement previously reported between the first excited analog levels is not confirmed. A total width $\Gamma =34\mathrm{}\pm 1$ keV is found for the level in ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$. The Doppler-shift limits are substantiated by observing a lifetime of 55±7 fsec for the 4.43-MeV level of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. For the 3.86-MeV level of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, a lifetime of ${9.0}_{-1.5\mathrm{}}^{+2.5\mathrm{}}$ psec is obtained.

• Received 6 June 1968

DOI:https://doi.org/10.1103/PhysRev.176.1140