双$K$壳层空位产生的单电子和双电子俘获衰变的比较研究
Comparative study of the double $K$-shell-vacancy production in single- and double-electron capture decay
摘要：
我们对$^{81}$ Kr的单$K$-壳层电子俘获和$^{78}$ Kr的双$K$-壳层电子俘获之后的双$K$-壳层空位产生的衰减信号进行了比较研究。通过检测$ECEC$ -衰变中的两个$K$ X射线和几个俄歇电子的三重符合，或者通过检测$EC$衰变中的两个$K$ X射线和（俄歇电子+喷射的$K$ -壳层电子），来识别双$1s$空位态的辐射衰变。对于$^{81}$ Kr的衰变，已经测量了由于甩脱过程产生的每个$K$ -电子捕获的$K$ -壳空位的数量。发现这种衰变的概率为$P_{KK}=(5.7\pm0.8)\times10^{-5}$，系统误差为$(ΔP_{KK})_{syst}=\pm0.4 \times10^{-5}$。对于$^{78}{\rm{Kr}}(2\nu2K)$衰变，单捕获和双捕获衰变的比较研究使我们能够获得信号背景比为15/1。在使用由170.6 g $^{78}$ Kr组成的样品的实验中，通过分析在782天的活体测量中积累的数据来确定$T_{1/2}^{2\nu2K}(g.s. \rightarrow g.s.) = [1.9^{+1.3}_{-0.7}(stat)\pm0.3(syst)]\times 10^{22}$ y的半衰期。
英文摘要：
We carried out the comparative study of the signal from the decay of double $K$-shell vacancy production that follows after single $K$-shell electron capture of $^{81}$Kr and double $K$-shell electron capture of $^{78}$Kr. The radiative decay of a the double $1s$ vacancy state was identified by detecting the triple coincidence of two $K$ X-rays and several Auger electrons in the $ECEC$-decay, or by detecting two $K$ X-rays and (Auger electrons + ejected $K$-shell electron) in the $EC$ decay. The number of $K$-shell vacancies per the $K$-electron capture, produced as a result of the shake-off process, has been measured for the decay of $^{81}$Kr. The probability for this decay was found to be $P_{KK}=(5.7\pm0.8)\times10^{-5}$ with a systematic error of $(ΔP_{KK})_{syst}=\pm0.4 \times10^{-5}$. For the $^{78}{\rm{Kr}}(2\nu2K)$ decay, the comparative study of single- and double-capture decays allowed us to obtain the signal-to-background ratio to be 15/1. The half-life $T_{1/2}^{2\nu2K}(g.s. \rightarrow g.s.) = [1.9^{+1.3}_{-0.7}(stat)\pm0.3(syst)]\times 10^{22}$ y is determined from the analysis of data that have been accumulated over 782 days of live measurements in the experiment that used samples consisted of 170.6 g of $^{78}$Kr.
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