Coulomb Effects and the O14 β-Decay Matrix Element

Abstract

The change of the Fermi matrix element of the β decay of O14 to the first excited state of N14 from its value sqrt[2] due to Coulomb corrections is reestimated. It is shown, that for pure 1p-shell states the reduction is between 0.02 and 0.20%. Configuration mixing in the 1p shell may increase these figures considerably. Instead of arbitrary admixtures of higher configurations, a collective model for the presumably most important of such admixtures is considered: The model of a "breathing state" (radial density oscillation). It is shown that for sufficiently low values of the energy of the first excited breathing state compatible with experimental data for the level spectrum of the mass-14 system, the β-decay matrix element may be reduced by as much as five percent. In view of the lack of present knowledge about the breathing state and nuclear compressibility for light nuclei, it is concluded that the discrepancy between the measured values of the vector and μ-meson decay coupling constants of β decay may well be due to such an effect.