Precision measurement of ${}^{210}$Bi $\beta$-spectrum

Abstract

The precision measurement of the $\beta -$spectrum shape for ${}^{210}$Bi (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 ${}^{210}$Pb background. The measured transition form-factor could be approximated as $S(W)=1+(-0.4363\pm 0.0037)W+(0.0523\pm 0.0010)W^2$, that is in good agreement with previous studies and has significantly increased parameter precision.

8 pages, 6 figures