Half-life of 60Fe

The half-life of ⁶⁰Fe has been measured to be $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= (1.49 ± 0.27) × 10}{}^6$ a, significantly longer than the one previous measurement of Roy and Kohman which reported a value of 3 × 10⁵ a uncertain by a factor of 3. The present value was obtained from measurements of specific activity and radioisotope concentration in a material produced by spallation of copper with 191 MeV protons. ⁶⁰Fe/Fe ratios in the range of 10^?8 were measured with the Argonne FN tandem-superconducting linear accelerator system in conjunction with an Enge split-pole spectrograph. The specific activity of ⁶⁰Fe in Fe was measured through the grow-in of the 1.332 MeV gamma-ray line of the ⁶⁰Co daughter activity.