Remeasurement of the half-life of Se-79 with the projectile x-ray detection method

Remeasurement of the half-life of Se-79 has been carried out with projectil e x-ray detection (PXD) in accelerator mass spectrometry. We made two major improvements over our earlier 79Se half-life determination [Nucl. Instrum. Methods B 123 (1997) 403]. Firstly, the PXD technique has been used for se paration of Se-79 and Se-75 from Br-79 and As-75 isobars respectively. Seco ndly, the half-life of Se-79 has been measured relative to the known precis e half-life of Se-75(119.79 +/- 0.04 d). A more reliable half-life of Se-79 measured with the PXD technique is (2.95 +/- 0.38) x 10(5) y, about a fact or of one third lower than the previous value, 1.1 x 10(6) y. The problems in the previous measurement are discussed.