A new value for the half-life of 10Be by Heavy-Ion Elastic Recoil Detection and liquid scintillation counting

The importance of Be-10 in different applications of accelerator mass spectrometry (AMS) is well-known. In this context the half-life of Be-10 has a crucial impact, and an accurate and precise determination of the half-life is a prerequisite for many of the applications of Be-10 in cosmic-ray and earth science research. Recently, the value of the Be-10 half-life has been the centre of much debate. In order to overcome uncertainties inherent in previous determinations, we introduced a new method of high accuracy and precision. An aliquot of our highly enriched Be-10 master solution was serially diluted with increasing well-known masses of Be-9. We then determined the initial Be-10 concentration by least square fit to the series of measurements of the resultant Be-10/Be-9 ratio. In order to minimize uncertainties because of mass bias which plague other low-energy mass spectrometric methods, we used for the first time Heavy-Ion Elastic Recoil Detection (HI-ERD) for the determination of the Be-10/Be-9 isotopic ratios, a technique which does not suffer from difficult to control mass fractionation. The specific activity of the master solution was measured by means of accurate liquid scintillation counting (LSC). The resultant combination of the Be-10 concentration and activity yields a Be-10 half-life of T-1/2 = 1.388 +/- 0.018 (1 s, 1.30%) Ma. In a parallel but independent study (Chmeleff et al. [11]), found a value of 1.386 +/- 0.016 (1.15%) Ma. Our recommended weighted mean and mean standard error for the new value for Be-10 half-life based on these two independent measurements is 1.387 +/- 0.012 (0.87%) Ma. (C) 2009 Elsevier B.V. All rights reserved.