重离子与原子分子碰撞过程中电荷交换反应绝对截面的精密测量

Cross section, being amongst the most important parameter in describing atomic collision processes, can point towards the relevant reaction mechanisms and also have been used as key physical quantities for checking many-body theories. On the other hand, cross sections for the interaction between ions and atoms play an important role in understanding astrophysical plasmas and fusion plasma diagnostics. However, due to the complicated collisional processes and high costs involved in experimental measurements, cross sections for highly charge ions interacting with atoms/molecules are still limited. In this project, based on the large scale accelerator HIRFL in Lanzhou, we plan systematic studies of the interactions between ions and atoms/molecules in the impact energy range of ~MeV. By measuring single and multiple electron capture absolute cross sections, we aim to determine electron capture cross sections as a function of impact energy. Using a reaction microscope, the three dimension momenta of the projectile ions, the recoil ions and the free electrons can be measured in multi-coincidence for the interaction of ions with atoms/molecules. Then both the transfer ionization cross sections and state-selective differential cross sections can be deduced. The systematic results expected from this project can help theorist to check the validity of their many-body theories and also can provide high accuracy atomic data for plasma physics.

截面是反映高电荷态离子与原子分子碰撞过程微观机制的重要参量之一，是检验理论模型可靠性的关键物理量。同时原子过程截面数据在天体等离子体和聚变等离子体研究中也具有重要意义。但由于高电荷态离子与原子分子作用过程复杂，实验成本高，碰撞过程中的绝对截面数据稀缺。本项目计划依托大科学装置HIRFL，在MeV能量范围内，系统地研究离子与原子分子作用过程。精确测量碰撞过程中的单电子和多电子俘获绝对截面，获得电子俘获截面随入射离子能量的变化规律。利用反应显微成像谱仪，采用散射离子、反冲离子和出射电子多重符合技术，获得反应产物的末态动量，根据动量、能量和电荷守恒，给出重离子与原子分子作用过程中的电荷转移截面，以及具有态选择的多重微分截面。为检验原子物理多体理论模型可靠性提供系统而丰富的实验数据，为等离子体研究提供高精度原子参数。

原子过程截面是理解和解释天体等离子体和聚变等离子体诸多现象的重要参数，是等离子体建模的基础，同时也是理解量子多体问题的关键物理量。本项目依托大科学装置HIRFL，在宽能域范围内，系统开展了高电荷态重离子与原子分子的碰撞实验，测量了电荷交换截面。具体包括：O6+离子与He、H2、N2、CO2和CH4碰撞中的单、双电子俘获绝对截面；Ne8+离子与He、H2、N2、O2和CH4碰撞中的单、双电子俘获绝对截面；Ne6+离子与He、H2、N2、O2和CH4碰撞中的单、双电子俘获绝对截面；He2+离子与He碰撞中的单、双电子俘获绝对截面，Ne8+、Ne9+、O6+、He2+、C4+和Fe9+离子与He碰撞中的电子俘获态选择截面，以及部分离子与H2分子碰撞中的电子俘获态选择截面。这些高精度的实验数据能够在绝对总截面、态选择微分截面、速度效应、电荷态效应等方面全方位检验高电荷态离子与原子分子碰撞现有理论模型的可靠性和适用范围，并可促进天体等离子体物理、聚变等离子体物理建模精度的提高，尤其为天文X射线发射谱的重构提供了重要的基准实验参数，按计划完成了研究目标。项目执行期间，发表文章16篇，其中标注为“第一资助”文章7篇，另有部分数据正在整理成文，将于近期发表。