电子与原子的碰撞电离是重要的微观物理过程，当前的研究前沿是直接多电离，它纯粹是由电子与电子之间的相互作用引起的高阶微扰过程，这一问题的研究对理解电子关联在碰撞过程中的作用很有价值，既有重要的科学意义，也在天体物理和等离子体物理中有应用价值。项目在原子碰撞理论基础上，发展描述电子与原子碰撞直接双电离的R-矩阵和扭曲波理论，研究直接双电离的微分和积分截面。对描述完整物理体系微观量子过程的跃迁几率幅进行多极散射级数展开，研究直接双电离发生的物理机制，根据物理机制的分离，研究三个连续电子的能量关联和关于电子能量的二重微分截面，并由此得到积分总截面。借鉴电子与原子碰撞直接双电离物理机制分离的物理思想，建立描述直接三电离过程中四个连续电子能量关联和电离总截面的理论。研究成果可望应用于非平衡等离子体电离平衡和辐射特性等领域。

Electron impact ionization of atoms is an important microscopic process in atomic physics. The next frontier is the direct multiple ionization, which is a higher order process due entirely to the electron-electron interaction. This subject has important scientific interest as well as practical applications in astrophysics and plasma physics. Based on the atomic collision theory, we develop close-coupling R-matrix and distorted wave methods to describe the direct double ionization of atoms by electron impact and obtain the differential and integrated cross sections. By expressing the probability amplitude of the direct double ionization process as a multiple scattering series, we identify the dominant mechanisms of shakeoff and two step processes, which can be used to investigate the energy correlation of the three continuum electrons. The method is extended to the direct triple ionization process. The atomic data are expected to be applied to astrophysics and plasma physics.