Shape of the β spectra in theA=14 system

We calculate the shape of the ${\mathrm{\beta }}^{\mathrm{-}}$ and ${\mathrm{\beta }}^{+}$ spectra in the A=14 system using constraints from measurements of the width of the M1 transition, ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$(e,${\mathit{e}}^{\prime }$) cross section, and logft values, as well as shell-model wave functions. Our result for the shape factor assuming conservation of vector current disagrees by a factor of 2 with existing data from ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ ${\mathrm{\beta }}^{+}$ decay.