激光调控重粒子碰撞中电荷转移机制理论研究

Heavy particle collisions exist ubiquitously in many fields, such as astrophysics and laboratory plasma, where the cross sections and rate coefficients are extremely important to plasma simulation and diagnostics. In this context, the investigation of influence of external fields on heavy particle collisions is of importance for both fundamental research and relevant applications. In this project, we solve the time-dependent Schrödinger equation by employing a multiconfiguration time-dependent Hartree (MCTDH) method to study ion-atom/molecule collisions at low energies, and on this basis we will investigate the mechanisms of laser field control of charge transfer in heavy particle collisions. First of all, in the framework of multireference configuration interaction, we carry out accurate calculations of electronic potential energy surfaces and non-adiabatic couplings and (transition and permanent) dipole moments for systems under study. Secondly, we develop a flux operator approach to extract and analyze the cross sections in the framework of MCTDH in order to study low-energy ion-atom/molecule collisions. Finally, we focus on the heavy particle collisions at low energies in the presence of linearly polarized laser fields by means of the MCTDH method. In this section, we will optimize laser parameters to study the mechanisms of laser manipulation on charge transfer of the proton(or hydrogen atom) colliding with a lithium atom. Furthermore, ion-molecule collisions illuminated by lasers will be studied, in which the influence of initial ro-vibrational states on the charge transfer will be revealed. The goal of this project is to preliminarily establish an effective strategy for the laser manipulation of charge transfer in heavy particle collisions.

重粒子碰撞普遍存在于天体物理和和实验室等离子体环境中，其反应截面和速率系数对等离子体模拟和诊断至关重要，因此研究外势场对重粒子碰撞影响具有重要的科学价值和应用意义。本项目拟采用多组态含时Hartree方法（MCTDH）求解含时薛定谔方程，研究低能离子-原子/分子碰撞过程，并探索激光对碰撞过程电荷转移影响和调控机制。首先，采用多参考组态相互作用方法精确计算碰撞体系的电子态势能面、耦合矩阵元和偶极跃迁矩阵元；其次，基于MCTDH框架，发展流算符方法提取反应截面，研究低能离子与原子/分子碰撞过程；最后，利用发展的MCTDH方法程序，研究激光场中低能离子-原子/分子碰撞过程，通过优化激光参数，探索激光调控氢离子-锂原子碰撞反应微观机理，并进一步探索激光调控离子-分子碰撞过程，研究初始振转态对激光调控电荷转移的影响。通过本项目研究，初步建立激光调控重粒子碰撞中电荷转移有效方案。

重粒子碰撞及调控是原子分子物理研究的热门课题之一，对等离子模拟和诊断很重要。本项目开展了激光调控重粒子碰撞中电荷转移机制理论研究，主要围绕无外场的重粒子碰撞和含激光场的碰撞过程。在重粒子碰撞方面，研究了低能碰撞诱导的共振态对不同通道激发的敏感性，发展了基于吸收边界条件提取电荷转移和电离总截面的方法，并在重粒子与分子的碰撞中得到了应用，建立了高电荷态离子与分子碰撞的电离量与解离通道的对应关系，定量评估了三体碎裂和四体碎裂的时间，分别为50-70飞秒和55-85飞秒，是为数不多从理论上计算给出重粒子碰撞多体碎裂的研究工作。加入激光场调控后，研究发现激光参数对电荷转移有较大影响，非绝热耦合作用能够导致更为复杂的结构。对于不同的延迟时间,在一定范围内适当的增大场强,可以有效地调控激发态；调整激光频率，共振激发的效率最高，同时电子布居数与激发能正相关；随着脉宽的增大，布居数单调递增；激光的延迟时间只有在零点时刻附近能够较为明显地改变共振态的宽度及线形。在一定范围内，通过优化激光参数，可以提高重粒子碰撞电荷转移的效率。本项目的研究工作对于实验上制备特殊离子态有一定的参考价值。