Absolute and relative measurement of the243Am half-life

The half-life of(243)Am has been measured by an absolute and a relative method, i.e. by determining the specific activity of(243)Am and the specific activity ratio with(241)Am. A mixed(241,243)Am reference material was produced and certified for its americium mass content and its isotope amount ratios. The characterisation of the mass content of(243)Am was established by isotope dilution mass spectrometry using an(241)Am spike, produced from highly enriched(241)Pu material. The isotope amount ratiosn(Am-241)/n(Am-243) andn(Am-242m)/n(Am-243) were measured by thermal ionisation mass spectrometry. Activity measurements were performed by alpha-particle counting at a defined solid angle, as well as high-resolution alpha-particle spectrometry. From the(243)Am/Am-241 activity and isotopic amount ratios, a value of 16.988 (24) was derived for the(243)Am/Am-241 half-life ratio. Using a value of 432.6 (6) a for the(241)Am half-life, the corresponding(243)Am half-life value, 7349 (15) a, is in good agreement with the result obtained from the absolute method, 7342 (14) a. The mean value, 7345 (14) a, agrees well with data from literature and lowers the relative standard uncertainty to 0.2%.