| Popis: |
A new attempt has been made for the re-measurement of the half-life of 79 Se. We made two major improvements over our earlier 79 Se half-life determination (Nucl. Instr. and Meth. B 123 (1997) 403). Firstly, the half-life of 79 Se was measured relative to the precisely known half-life of 75 Se, rather than an absolute measurement of 79 Se/Se. Secondly, the Projectile X-ray Detection technique was used for the separation of 79 Se from its isobar, 79 Br, rather than measuring 81 Br for the deduction of 79 Br interference, and this technique was also used for separation of 75 Se and its isobar, 75 As. A detailed description of the sample preparations, experimental setup and measurements are given. The re-measured half-life of 79 Se was (2.95±0.38)×10 5 a, about a factor of 3 lower than the previous value, 1.1×10 6 a. The problems in the previous measurement are discussed. |
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