低能He^(2+)与He原子碰撞转移电离出射电子能谱研究

Investigation on Electron Energy Spectra of Transfer Ionization Process in 70 and 100 keV He^(2+) Colliding on He

利用反应显微成像谱仪对70和100keV He2+与He原子碰撞转移电离(TI)过程中不同出射角度的电子能谱进行了测量,观测到出射电子能谱具有如下分布特征:出射电子速度分布介于0和入射离子速度vp之间;在不同出射角度电子能谱分布均有一极大值存在,随着出射角度的增大,能谱分布极大值逐渐减小;当电子出射角度等于45°时,多数电子集中在0eV附近。上述特征可由低能离子-原子碰撞"准分子"模型进行定性解释。在100keV He2+-He转移电离出射电子能谱中有靶电子被俘获至散射离子连续态(electron capture to continuum,简称ECC)电子的贡献,这可看做是动力学两步过程的作用。

The energy spectra of emitted electrons in transfer ionization process of 70 and 100 keV He2＋ colliding on He haev been measured by using Reaction Microscope.The energy spectra of the ejected electrons have been obtained in the angular range from 0° to 45° and energies from 0 to 45 eV.The characteristics of the energy spectra were analyzed.There is a maximum in each energy spectrum related to different emission angles;The position of the maximum decreases with increasing the emission angle;The velocity of emitted electrons is between 0 and vp,where vp is the projectile velocity;Most electrons are around 0 eV when electron emission angle is 45°.These characteristic could be qualitatively explained in a ＂quasimolecule＂ model.The ECC electrons were observed in the transfer ionization process of 100 keV He^2＋ colliding on He collision,It could be explained as dynamical two-step process.