K-capture in carbon 11

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Abstract
K-capture in 11C has been observed and the K/β+ ratio found. Comparison with theory leads to a value for the ratio of the Fermi coupling constants. Proportional counters were employed with a gaseous source, and two anti-coincidence systems were used, in turn, to reduce wall effects. One made use of a multi-wire ring type counter and the other utilized an envelope of scintillating material coupled to a photomultiplier. The K/β+ ratio has been determined at (1.9±0.3) × 10−3, and accords closely with the theoretical value baaed on the vanishing of interference terms. A comparison shows that the factor b in beta-decay theory, which determines the ratios of decay coupling constants, is (−0.03±0.10). In this decay between mirror nuclei the Fermi matrix element predominates, and the ratio of the two Fermi coupling constants Cv/Cs has been deduced at (−0.02±0.09), from data on the better known Gamow-Teller constants. The pulse height distribution obtained in these experiments showed that little ionization was produced by the nuclear recoil following neutrino emission, though the recoil energy could be comparable with the 180 ev capture x-ray energy.