A NEW DETERMINATION OF THE HALF-LIFE OF SI-32

The half-life of Si-32 has been redetermined. A value of 133 +/- 9 yr was obtained from different Si-32-samples produced by proton activation of Cl-37 (as LiCl) and neutron activation of P-31 (as Mg2P2O7). After chemical separation, purification and conversion to K2SiF6, the specific activity of Si-32 was measured by liquid scintillation counting. Additional chemical treatments were used to test the radiochemical purity of the samples. The Si-32/Si(tot) ratio was measured by accelerator mass spectrometry (AMS). To determine and correct for the mass fractionation in the tandem accelerator system, the four silicon isotopes Si-28, Si-29, Si-30 and Si-32 were measured quasi-simultaneously under as identical conditions as possible. Special care was taken to estimate the contributing uncertainties for the determinations of both the specific activity and the isotopic ratio.