The 3$alpha$ decay of the 16.62,MeV (2$^-$, T=1) resonance in $^{12}$C has been studied for nearly a century starting with one of the first nuclear reaction studies at the Cavendish Laboratory in the 1930s. In the hitherto latest study published a de
cade ago a model based on earlier work from the 1960s was found to give a good account of a set of inclusive data. This model describes the decay as an l=3 $alpha$-particle populating the 2$^+$ state of $^8$Be. Here we provide new exclusive data on the 3$alpha$ decay of the 16.62,MeV resonance, and demonstrate that the decay is best described by a model with predominantly l=1 emission with an admixture of l=3.
The 16.1MeV 2+ resonance in 12C situated slightly above the proton threshold can decay by proton-, $alpha$-, and $gamma$ emission. The partial width for proton emission cannot be directly measured due to the low proton energy and the small branching
ratio. Instead it must be indirectly derived from other observables. However, due to several inconsistent data the derived partial width varies by almost a factor 2 dependent on the data used. Here we trace the majority of this inconsistency to different measurements of the $(p,alpha)$ cross sections. We have remeasured this cross section using modern large area silicon strip detectors allowing to measure all final state particles, which circumvents a normalization issue affecting some of the previous measurements. Based on this we determine $Gamma_{p}$ = 21.0(13)eV. We discuss the implications for other observables related to the 16.1 MeV $2^{+}$ resonance and for isospin symmetry in the $A=12$ system. In addition, we conclude that the dataset currently used for the NACRE and NACRE II evaluation of the $^{11}mathrm{B}(p,3alpha)$ reaction should be scaled by a factor of 2/3. This impacts the reaction rate accordingly.
