A theoretical study on electon-capture process by multiply-charged ion in external magnetic field

1.在外加磁场的影响下，建立了离子-原子碰撞中电子俘获过程的半经典紧耦合方程，其中磁场的方向与入射粒子的速度成任意关系。该公式已应用于某些系统，即，（B^<4+>+H）、（Be^<2+>+H）、（Be^<3+>+H）和（He^<2+>+H）。通过这些计算得到的主要结果如下。(1)一般来说，磁场使电子捕获加速，但对于某些状态和/或在某些角度下，也有截面减小的情况。(2)当磁场方向垂直于碰撞平面时，由于磁场和转动耦合的共同作用，磁场效应最强。(3)在磁场与入射速度之间的角度上积分的截面随着磁场的增加而缓慢增加。(4)2.研究了极化效应，即运动的多电荷离子极化靶与磁场相互作用的效应。3. He^<2+>+H（1 s）*He^+（2l）+H^+过程对应于共振情况，并预测了磁场的类混沌效应的可能性。然而，在这种情况下，发生两种类型的转变，一种是由于斯塔克混合的相位，另一种是由于旋转耦合。在很大的核间距下的跃迁使得跃迁机制非常复杂。我们已经做了一个计算程序，现在正在使用它进行计算。

1.A semiclassical close-coupling equation is formulated for the electron-captureprocess in ion-atom collisions under the influence of an external magnetic field where the field direction was arbitrary to the incident projectile velocity. This formula has been applied to some systems, i.e., (B^<4+>+H), (Be^<2+>+H), (Be^<3+>+H), and (He^<2+>+H). The main results obtained by these calculations are as follows.(1) In general, the magnetic field make the electron capture accelerate, but for some states and/or at certain angle there are cases also where the cross sections decrease.(2) The magnetic field effect is the most strong when the direction of the magnetic field is perpendicular to the collision plane, because of the cooperetive action of magnetic field and rotational coupling.(3) The cross sections integrated over angle between the magnetic field and the incident velocity increase slowly with magnetic field.(4) The lower the collision energy becomes, the more effective the magnetic field becomes.2.We investigated the polarization effect, that is, the effect of the interaction between polarized target by moving multiply charged ion and magnetic field. However, this effect is pretty small in our cases.3.The process, He^<2+>+H (1s)*He^+ (2l) +H^+, is corresponding to a resonance case and the possibility of chaos-like effect of magnetic field is predicted. However, in this case, there occurs two-type transitions, one is that due to phase by the Stark mixing and the other is that due to the rotational coupling. The transition at very large internuclear distance makes the transition mechanism very complex. We have made a proguram and are now performing calculatious using it.