Demonstration of the Need for Meson Exchange Currents in the Beta Decay ofN16(O)

Abstract
The N16(0, 120 keV)O16(0+,g.s.)+e+ν̃e beta decay rate is remeasured. The present result, Λβ=0.41±0.06 sec1, agrees with recent realistic calculations of this rate only when pion exchange currents are included in the axial-vector time component. The impulse approximation underestimates this rate by more than a factor of 3. This result may be combined with the muon capture rate for the inverse reaction to obtain gPgA=10±2.5.