低能He^2＋-He反应中单电子俘获微分散射过程的实验研究

Experimental differential investigation of state-selective single electron capture in slow He^(2+)-He collisions

利用冷靶反冲离子动量谱仪装置系统研究了20—40keVHe2+-He碰撞体系的态选择单电子俘获过程,实验获得了单电子俘获过程的态选择截面以及角微分截面.在所研究的能区范围,电子俘获到L壳层的截面最大,为主要的反应道,这与分子库仑过垒模型的反应窗理论的预测一致.实验测量的态选择截面与原子轨道紧耦合的计算结果很好地符合,与光谱方法的测量结果存在一定的差别,主要原因是光谱方法不能测量完整的反应通道信息.实验结果表明,总角微分截面在小角度范围主要来源于电子俘获到基态的贡献,在大角度范围主要来自电子俘获到激发态的贡献;电子俘获到基态的和激发态的角微分截面均出现振荡结构,这种振荡来源于电子俘获反应中分子轨道之间的相干效应.实验测量的角微分截面与其他实验和紧耦合方法的计算结果进行了比较和分析.

State-selective single electron capture in He 2＋-He collisions at energies ranging from 20 to 40 keV have been studied experimentally by means of cold target recoil ion momentum spectroscopy. The differential cross sections have been obtained by measuring the longitudinal and transverse momenta of recoil ions. The results show that single electron capture into L shell is the dominant reaction channel,which was qualitatively explained with reaction window theory. The measured state-selective cross sections agree with the semi-classical close-coupling calculations,but have some deviations from the results of photon emission measurement. Total angular differential cross sections show that the single electron capture into ground state mainly contributes at small angles,and the single electron capture into excited states contributes at large angles. The oscillating structures of angular differential cross sections are observed,and can be understood by the interference of molecular orbits during the collision processes. The measured angular differential cross sections are compared with other experiments and the quantum-mechanical calculation.