Analysis of the Beta Spectrum and Branching inHo166

The shape of the $\beta$ spectrum of the ${\mathrm{Ho}}^{166}$→${\mathrm{Er}}^{166}$ ground state (0- → 0+) transition and the branching to the first excited state (2+) has been investigated. Corrections due to the variation of the lepton wave functions over the nucleus have also been taken into account, and it is shown that under certain conditions these corrections can be sufficient to explain the experimental findings.