The precision measurement of the β−spectrum shape for 210Bi (historically RaE) have been performed with a spectrometer based on semiconductor Si(Li) detector. This first forbidden non-unique transition has the transition form-factor strongly deviated from unity and knowledge of its spectrum would play an important role in low-background physics in presence of 210Pb background. The measured transition form-factor could be approximated as S(W)=1+(−0.4363±0.0037)W+(0.0523±0.0010)W2, that is in good agreement with previous studies and has significantly increased parameter precision.
@article{arxiv.2005.08481,
title = {Precision measurement of $^{\mathbf{210}}$Bi $\beta$-spectrum},
author = {I. E. Alekseev and S. V. Bakhlanov and A. V. Derbin and I. S. Drachnev and I. M. Kotina and I. S. Lomskaya and V. N. Muratova and N. V. Niyazova and D. A. Semenov and M. V. Trushin and E. V. Unzhakov},
journal= {arXiv preprint arXiv:2005.08481},
year = {2021}
}