CO2单电离及电离解离过程的(e,2e+ion)实验研究

Electron induced ionization and dissociation of CO2 is not only a basic process for understanding of the collision dynamics, but also draws great interest in numerous application fields, such as plasma physics and chemistry of atmospheres. Charged particles including one ion and two electrons are produced during such processes. If all of those charged particles are imaged in triple coincidence (i.e. the so called (e, 2e+ion) experiment), much detailed information can then be deduced for the investigation of the collision process. We plan to carry out such a (e, 2e+ion) study using the Reaction Microscope in Lanzhou. In such an experiment, the momentum of all charged particles can be calculated, and thus differential cross sections, which may reveal the collision dynamics, can be produced. Special attention would be spent on the influence of molecular configuration for the dynamics of the single ionization process, and the dependence of the fragmented ions (species and kinetic energy distributions etc.) on the energy deposited into the target during the collision.

电子碰撞导致的CO2分子单电离及电离解离过程研究不仅具有重要的基础物理意义，同时在等离子体物理、大气化学等领域中有应用价值。该过程中会产生两个电子和一个离子，对末态的所有出射电子和离子进行三重符合测量（即(e, 2e+ion)实验），将为探索碎裂过程的动力学机制提供非常详细的信息。本项目拟利用中科院近代物理所的反应谱仪完成CO2分子的(e, 2e+ion)实验，通过重构所探测粒子的动量获得描述反应过程的各种微分截面，详细进行以下两方面研究：1，对单电离过程,利用描述出射电子角分布的三重微分截面，研究分子构型对电离过程中电子出射特征的影响；2，对电离解离过程,通过还原末态出射电子的动能，确定碰撞过程中沉积到靶分子中的能量，从而探究碎片离子种类及动能分布与沉积能的关联性。

在本项目的资助下，我们建成了用于电子碰撞导致原子、分子电离或解离过程研究的反应谱仪。本装置和德国马普核物理所的(e, 2e)谱仪是世界上仅有的两台能够对电子碰撞电离末态中电子和离子进行多重符合探测的反应谱仪。我们用该装置研究了电子碰撞导致CO2、CH4等分子的电离及解离过程，实验获得了与各个离子碎片相对应的反应Q值，从而确定了对这些离子碎片有贡献的离子态；获得了电离过程的全微分截面，研究了分子构型等因素对微分截面的影响。我们还在标准反应谱仪的基础上增加光子探测，以对末态产物中光子-电子-离子进行多重符合探测，从而实现了对He原子电离激发过程末态产物中角动量量子数的区分。