三维离子成像技术研究里高密度德堡态NO分子产生的超低温等离子体空间结构及膨胀过程

The spontaneous ionization of dense Rydberg molecules in a molecule beam could form ultracold plasma. Ultracold plasma is one of the most promising methods to reach the strongly coupled regime, which is helpful for intense field physics, astrophysics and nuclear fusion as its possibility to create a controllable and detectable strongly coupled system. Experimental methods to prepare much denser and colder plasma and expand its lifetime are valuable for strongly coupled research, which together with ultracold plasma evolution dynamic process are important targets in this new field. We will study the preparation and detection methods of ultracold plasma in a supersonic molecule beam, and the possibility to inhibit its heating process by the use of Rydberg molecules. A novel movable time-sliced ion imaging technology will be used to monitor the 3D intensity distribution of ultracold plasma and its variation with delay time, and the expansion process will be studied by this novel method. The presence of anions slows the disorder induced heating and three body recombination, and finally slows the expansion velocity of UCP. However, the operation mechanisms of these heating process are distinct in principle, and their influence resulting from the presence of anions are different .luckily, the anions formation efficiency could be affected by the NO molecule density and the energy of excited photons, so we could research the effect mechanisms of these two heating processes through varying the anions quantity and percentage in UCP. With the assistance of molecular dynamics and thermodynamic model analysis, the result can be used to describe ultracold plasma heating and expansion mechanism. All the studies aim to offer experimental methods on strongly coupled ultracold plasma preparation and detection, and theoretical test and improvement, which could also be helpful for strongly coupled problems.

高密度低温里德堡态分子（原子）的自发演化可以形成超低温等离子体（Ultracold plasma，UCP），UCP 能模拟天体环境、热核聚变和反物质产生过程中的强耦合现象，为这些极端环境中的动力学过程研究提供帮助。研究UCP 的膨胀演化过程及影响因素，对维持等离子体的强耦合状态非常有利，进而有助于上述重大基础问题的研究。目前我们已搭建了一套在分子束中产生超低温等离子体的实验装置，并产生了具有一定耦合强度的超低温等离子体。本项目拟建立一种适用于分子束中高速运动的超低温等离子体的三维成像探测方法，研究超低温等离子体的空间结构及膨胀演化过程；通过调整UCP中负离子的产率，改变UCP中无序诱导加热和三体复合加热的作用速率及权重，结合理论建模工作，研究负离子影响超低温等离子体膨胀过程的规律。旨在探索超低温等离子体的内部结构及演化规律，验证并完善超低温等离子体的膨胀演化动力学理论。

高密度超低温里德堡态分子（原子）的自发演化可以形成超低温等离子体（Ultracold plasma，UCP），UCP 能模拟天体环境、热核聚变和反物质产生过程中的强耦合现象，为这些极端环境中的动力学过程研究提供帮助。研究UCP 的膨胀演化过程及影响因素，对维持等离子体的强耦合状态非常有利，进而有助于上述重大基础问题的研究。研究ＵＣＰ中的带电粒子种类、构成及其产生机制，对于探索认识UCP的形成机理、初始状态进而研究UCP 的膨胀演化过程至关重要，本项目的主要目的就是通过研究UCP产生初期及一段时间内UCP中的带电粒子类型及相对浓度等，研究UCP的形成机理及演化膨胀过程。目前我们已搭建了一套在分子束中产生超低温等离子体的实验装置，并在不同的实验条件下产生了具有一定耦合强度的超低温等离子体。本项目设计并初步建立一种适用于分子束中高速运动的超低温等离子体的三维成像探测方法，研究超低温等离子体的空间结构及膨胀演化过程。我们在试验中通过改变激发光的波长，改变NO分子共振激发的中间能级，进而改变初始时刻电子的能量分布，获得了一定数量并且密度可以在一定程度控制的负离子，改变了UCP 中无序诱导加热（DIH）和三体复合（TBR）加热的作用速率及权重，结合理论建模工作，研究了负离子影响超低温等离子体膨胀过程的规律。本项目还研究了超低温等离子体中负离子的产生机制，综合分析前人理论实验工作的基础上，提出了超低温等离子体中一种新型的负离子产生机制—电子附着电离（dissociative electron attachment），对正负离子组成的超低温等离子体的扩散过程及其寿命进行了理论及实验分析，为超低温等离子体的膨胀演化动力学理论研究提供了支持。