The 4p 6 excitation-autoionization (EA) cross-section of Sr atoms has been measured at electron-impact energies from the threshold to 600 eV. The cross-section has a pronounced resonance character in the near-threshold region, reaching its maximum value of (2.5 ± 0.8) × 10 −16 cm 2 at 24.5 eV. The shape and absolute value of the cross-section are determined by the excitation dynamics and the decay mode of autoionizing states from 4p 5 4d5s 2 , 4p 5 4d 2 nl and 4p 5 4d5s nl configurations. A comparative analysis of the measured EA cross-section, the calculated 5s 2 ionization cross-section and the available ionization data showed that (i) direct ionization of the 5s 2 shell and EA of the 4p 6 shell adequately describe the single ionization of Sr atoms; (ii) 4p 6 EA contribution reaches 25% of the total single ionization cross-section of Sr atoms.

中文翻译：

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激发自电离对电子碰撞引起的Sr单电离的贡献

Sr原子的4p 6激发自电离（EA）截面是在从阈值到600 eV的电子碰撞能量下测量的。该横截面在近阈值区域具有明显的共振特性，在24.5 eV时达到（2.5±0.8）×10 -16 cm 2的最大值。横截面的形状和绝对值由4p 5 4d5s 2，4p 5 4d 2 nl和4p 5 4d5s nl配置的激发动力学和自电离态的衰减模式确定。对测得的EA横截面，计算出的5s 2电离横截面和可用电离数据的比较分析表明：（i）5s 2壳的直接电离和4p 6壳的EA足以描述Sr的单次电离原子 （ii）4p 6 EA的贡献达到Sr原子单离子总横截面的25％。