LIFETIMES OF LEVELS IN 12C 13C AND 13N

The Doppler-shift method is used to obtain lifetime limits of τ<10 fsec and τ<26 fsec for the 3.09- and 3.68-MeV levels of C13, respectively. The radiative width Γγ is remeasured for the 2.37-MeV state of N13 in the reaction C12(p,γ)N13 and found to be 0.45±0.05 eV, corresponding to τ=1.47±0.15 fsec. Thus, the disagreement previously reported between the first excited analog levels is not confirmed. A total width Γ=34±1 keV is found for the level in N13. The Doppler-shift limits are substantiated by observing a lifetime of 55±7 fsec for the 4.43-MeV level of C12. For the 3.86-MeV level of C13, a lifetime of 9.0-1.5+2.5 psec is obtained. © 1968 The American Physical Society.