The half-life of 243Am has been measured by an absolute and a relative method, i.e. by determining the specific activity of 243Am and the specific activity ratio with 241Am. A mixed 241,243Am reference material was produced and certified for its americium mass content and its isotope amount ratios. The characterisation of the mass content of 243Am was established by isotope dilution mass spectrometry using an 241Am spike, produced from highly enriched 241Pu material. The isotope amount ratios n(241Am)/n(243Am) and n(242mAm)/n(243Am) 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 243Am/241Am activity and isotopic amount ratios, a value of 16.988 (24) was derived for the 243Am/241Am half-life ratio. Using a value of 432.6 (6) a for the 241Am half-life, the corresponding 243Am 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%.

中文翻译：

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243Am 半衰期的绝对和相对测量

243Am 的半衰期已通过绝对和相对方法测定，即通过确定 243Am 的比活度和与 241Am 的比活度比值。生产了一种混合的 241,243Am 参考材料，并对其镅质量含量和同位素含量比进行了认证。243Am 的质量含量的表征是通过同位素稀释质谱法建立的，使用 241Am 尖峰，由高度富集的 241Pu 材料制成。同位素量比n(241Am)/n(243Am)和n(242mA)/n(243Am)通过热电离质谱法测量。活动测量是通过在定义的立体角下进行 α 粒子计数以及高分辨率 α 粒子光谱法来进行的。从 243Am/241Am 活度和同位素量比值来看，值为 16。988 (24) 是由 243Am/241Am 半衰期比得出的。对于 241Am 半衰期使用 432.6 (6) a 值，相应的 243Am 半衰期值 7349 (15) a 与绝对方法获得的结果 7342 (14) a 非常吻合。平均值 7345 (14) a 与文献数据非常吻合，并将相对标准不确定度降低至 0.2%。