Alpha-decay Rates of Yb and Gd in Solar Neutrino Detectors

Abstract

The $α$-decay rates for the nuclides $^{168,170,171,172,173,174,176}$Yb and $^{148,150,152,154}$Gd have been estimated from transmission probabilities in a systematic $α$-nucleus potential and from an improved fit to $α$-decay rates in the rare-earth mass region. Whereas $α$-decay of $^{152}$Gd in natural gadolinium is a severe obstacle for the use of gadolinium as a low-energy solar-neutrino detector, we show that $α$-decay does not contribute significantly to the background in a ytterbium detector. An extremely long $α$-decay lifetime of $^{168}$Yb is obtained from calculation, which may be close to the sensitivity limit in a low-background solar neutrino detector.