【作者】 邵剑雄；

【导师】 陈熙萌；

【作者基本信息】 兰州大学 ， 粒子物理与原子核物理， 2007， 博士

【摘要】 本工作在兰州大学2×1.7MV串列加速器上利用0.2MeV～5.8MeV的C^q+、O^q+（q=1、2、3）入射离子与He原子进行碰撞，对碰撞中的多重电离过程进行了研究。实验上采用反冲离子—散射离子飞行时间符合技术、位置灵敏探测技术及多参数获取系统得到散射离子与反冲离子电荷态的二维符合谱，从而得到不同入射离子的单双电离截面比的随入射离子能量变化的曲线。实验结果表明，对于直接电离过程和转移电离过程，单双截面比的实验值有下列几个共同的特点：（1）当入射离子能量开始大于几十个keV/amu时，单双电离截面比随着入射离子能量的增加而迅速增加。（2）当入射离子能量大约为200～300keV/amu时，单双电离截面比达到最大值。（3）过了最大值之后，随着入射离子能量继续增加，单双电离截面比缓慢下降。在理论上，从只考虑电子俘获过程的Bohr经典过垒模型出发，考虑电子从分子态的直接电离问题，把中低能区的俘获和电离放在一个框架内考虑。理论计算结果比较好的说明了实验数据的主要特征。更多还原

【Abstract】 Single and double ionization of Helium induced by C^q+,O^q+（q=1-3） ions were studied both in experiment and in theory. The double-to single-ionization ratios R were measured by coincidence between time of flight （TOF） and position information. The energy of these ions ranges from 0.2MeV to 5.8MeV. This work was performed on the 2×1.7MV tandem accelerator in Lanzhou University.The experimental results indicated that when the collision energy is about 200 or 300keV/amu, the value of R reaches the maximum, not only in the direct ionization process, but also in the charge exchange process. Meanwhile, a new theory model, based on the classical over-the-barrier model is performed, which aims to include the ionization process.The comparison between the different experimental values and the theoretical calculation shows a qualitative agreement, in particular showing a maximum occurring at about 250 keV/amu.更多还原