Search for the decay of nature's rarest isotope ~(180m)Ta

摘要

~(180)mTa is the rarest naturally occurring quasistable isotope and the longest lived metastable state which is known. Its possible decay via the β~- or the electron capture channel has never been observed. This article presents a search for the decay of 180mTa with an ultralow background Sandwich HPGe γ spectrometry setup in the HADES underground laboratory. No signal is observed and improved lower partial half-life limits are set with a Bayesian analysis to 5.8 × 10~(16) yr for the β~- channel and 2.0 × 10~(17) yr for the electron capture channel (90 % credibility). The total half-life of 180mTa is longer than 4.5 × 10~(16) yr. This is more than a factor of two improvement compared to previous searches.