A search for radioactivity among the naturally occurring isobaric pairs

Assessment of the 187Re decay constant by cross calibration of Re–Os molybdenite and U–Pb zircon chronometers in magmatic ore systems

“…Many studies used direct counting experiments and determined k 187 Re values between 2.31 · 10 À11 and 1.39 · 10 À13 a À1 (Sugarman and Richter, 1948;Suttle and Libby, 1954;Watt and Glover, 1962;Wolf and Johnston, 1962;Brodzinski and Conway, 1965;Naldrett, 1984;Ashktorab et al, 1993;Alessandrello et al, 1999;Galeazzi et al, 2001;Arnaboldi et al, 2003) ( Table 1). The precision of these studies has been improved by mircocalorimetric determinations (Ashktorab et al, 1993;Alessandrello et al, 1999;Galeazzi et al, 2001;Arnaboldi et al, 2003), but even these modern methods yield results with uncertainties at the several percent level (Galeazzi et al, 2001).…”

New limits on naturally occurring electron capture of123Te

“…In a more recent and detailed paper, O. Civitarese and J. Suhonen [20] note that a suppression of the nuclear matrix element of the second-forbidden EC transition of this * CEE fellow in the Network on Cryogenic Detectors, under contract FMRXCT980167 nucleus is a very severe test of the nuclear models used to calculate rare electroweak decays. One of the claimed experimental evidences of the decay [15] is in contradiction with this thoretical model. A precise measurement of the 123 Te decay rate can therefore shed light both on the experimental situation and on the mechanisms which are at the basis of the above mentioned cancellation.…”

“…Evidence for the K EC decay of 123 Te was obtained by Watt and Glover [15] with a lifetime t K 1/2 = (1.24±0.10)× 10 13 years, using a proportional counter. Such a value is still reported in the Nuclear Tables [16].…”

“…Contradictory experimental results have been in fact presented [15,17]. Very low rates have been, on the other hand, predicted theoretically on the basis of a strong suppression of the nuclear matrix elements due to a cancellation between particle-particle and particle-hole correlations.…”

“…It has been actually detected in seven of them [2,3,4,5,6,7,8,9,10,11,12,13], while no evidence has been found for beta decay of the 9 − excited state of 180 Ta [14]. More complex is the situation [15,16,17,18] for the second forbidden unique electron capture (EC) of 123 Te to the ground state of 123 Sb, with a transition energy of 53.3 ± 0.2 keV (Q EC ).…”