Smallest known Q value of any nuclear decay: the rare beta;{-} decay of ;{115}In(9/2;{+}) --> ;{115}Sn(3/2;{+}).
The ground-state-to-ground-state Q_{beta;{-}} value of ;{115}In was determined to 497.68(17) keV using a high-precision Penning trap facility at the University of Jyväskylä, Finland. From this, a Q_{beta;{-}} value of 0.35(17) keV was obtained for the rare beta;{-} decay to the first excited state of ;{115}Sn at 497.334(22) keV. The partial half-life was determined to 4.1(6) x 10;{20} yr using ultra low-background gamma-ray spectrometry in an underground laboratory. Theoretical modeling of this 2nd-forbidden unique beta;{-} transition was also undertaken and resulted in Q_{beta;{-}} = 57_{-12};{+19} eV using the measured half-life. The discrepancy between theory and experiment could be attributed to atomic effects enhanced by the low Q value. The present study implies that this transition has the lowest Q value of any known nuclear beta decay.
EC-JRC-IRMM, Institute for Reference Materials and Measurements, B-2440 Geel, Belgium.
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Wieslander
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Suhonen
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Eronen
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Hult
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Elomaa
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Jokinen
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Marissens
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Misiaszek
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Mustonen
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Rahaman
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Weber
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Aystö