The half-life of 22Na has been determined through 523 activity measurements over 14.5 years with a re-entrant ionisation chamber in a temperature-stabilised room. The data were selected and aggregated from in total 127 830 ionisation current measurements with a reproducibility of the order of 0.065% standard deviation. The ionisation current was collected over an air capacitor and measured as a change of voltage over time, which warrants excellent linearity with activity throughout the experiment. The residuals to an exponential decay curve show a distinct annual cycle of 0.0055 (5)% amplitude, which reduces to 0.0012 (5)% after compensation for a correlation with ambient humidity. The data confirm the validity of the exponential-decay law, in absence of cyclic perturbations at daily, monthly, and multi-annual scale at the level of 0.0005% standard deviation. The 22Na half-life value obtained in this study is 950.68 (12) d or 2.60290 (34) a, with a relative standard uncertainty of 0.013%. This value is consistent with the mean value of other measurement results in the literature, although the latter have an issue with incomplete uncertainty budgets. Owing to the high statistical accuracy and conservative uncertainty estimate of systematic errors, the result obtained in this work can be recommended as a reliable reference value.

中文翻译：

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22Na 半衰期的测量和支持指数衰变定律的证据


22Na 的半衰期是通过 523 年的 14.5 次活性测量确定的，该电离室位于温度稳定的房间中。数据是从总共 127 830 次电离电流测量中选择和汇总的，重现性约为 0.065% 标准偏差。电离电流通过空气电容器收集，并测量为电压随时间的变化，这保证了整个实验过程中与活性的出色线性度。指数衰减曲线的残差显示 0.0055 （5）% 振幅的明显年周期，在补偿与环境湿度的相关性后，该振幅降低到 0.0012 （5）%。数据证实了指数衰减定律的有效性，在每日、每月和多年尺度上没有 0.0005% 标准差水平的周期性扰动。本研究获得的 22Na 半衰期值为 950.68 （12） d 或 2.60290 （34） a，相对标准不确定度为 0.013%。该值与文献中其他测量结果的平均值一致，尽管后者存在不确定性预算不完整的问题。由于统计精度高，系统误差的保守不确定性估计，本研究获得的结果可以作为可靠的参考值。