Two-step single-ionization mechanisms
Two-step single-ionization mechanisms
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DOI：
10.1103/physreva.73.032703
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发表时间：
2006-03
影响因子：
2.9
通讯作者：
R. W. Boeyen;N. Watanabe;J. Cooper;J. P. Doering;J. Moore;M. Coplan
中科院分区：
文献类型：
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作者：
R. W. Boeyen;N. Watanabe;J. Cooper;J. P. Doering;J. Moore;M. Coplan
在最近的一份出版物中[Phys.莱特牧师。92,233202(2004年)]确定了两种不同的电子碰撞双电离(e，3e)机制，并讨论了通过三重符合(e，3e)测量获得原子和分子的双电子动量分布的方法。所用的仪器以45度角探测到散射面内外的两个抛射电子。到与散射电子三重重合的动量转移方向。从散射面探测到的抛射电子被证明是两步双电离过程的结果。为了获得更多关于两步电离的信息，我们用同一装置对入射能量从400 eV到3000 eV的镁3S(价)电子和2P和2S(内)壳层电子的电子碰撞单电离截面进行了双符合(e，2e)测量。将实验结果与二阶扭曲波和平面波Born近似进行了比较。在实验条件下，包括与原子核的一次电离碰撞和二次弹性碰撞的两步电离过程对测量截面的贡献占主导地位。计算结果与数据有一定的一致性。这些两步电离中电离电子的角分布反映了目标电子的初始动量分布，这一结果与早期的(e，3e)测量结果类似。
In a recent publication [Phys. Rev. Lett. 92, 233202 (2004)] two different electron impact double ionization (e,3e) mechanisms were identified and the way in which two-electron momentum distributions for atoms and molecules could be obtained by triple coincidence (e,3e) measurements was discussed. The apparatus used detected the two ejected electrons both in and out of the scattering plane at an angle of 45 deg. to the momentum transfer direction in triple coincidence with the scattered electron. Ejected electrons detected out of the scattering plane were shown to be a result of two-step double ionization processes. With the same apparatus we have made double coincidence (e,2e) measurements of electron impact single ionization cross sections for ionization of magnesium 3s (valence) and 2p and 2s (inner) shell electrons at incident energies from 400 to 3000 eV in order to obtain more information about two-step ionization. The experimental results were compared with distorted-wave and plane-wave Born approximations carried out to second order. For the experimental conditions, two-step ionization processes involving one ionizing collision and a second elastic collision with the atomic core are the dominant contribution to the measured cross sections. Calculations are in moderate agreement with the data. The angular distributions ofmore » the ionized electrons in these two-step ionizations reflect the initial momentum distributions of the target electrons, a result that is analogous with the earlier (e,3e) measurements.« less