发射光谱诊断是一种常用而且非常重要的等离子体诊断方法。它不影响等离子体的放电状态，不受等离子体中的射频电场或磁场的干扰，测量发射光谱的实验设备也比其他诊断方法简单。然而，从测量的光谱数据中分析出等离子体参数是一个复杂的过程，需要一个能正确地描述激发态粒子的主要动力学过程的碰撞辐射模型来计算光谱与等离子体参数之间的关系。这种基于正确模型的发射光谱诊断方法正是目前国际低温等离子体研究领域所欠缺和需要的。 为解决这一问题，本文对多种低温等离子体进行了光谱测量、等离子体诊断和碰撞辐射模型研究。借助实验检验，给出了氩和氮低温等离子体的“简单碰撞辐射模型”，以及相应的新的发射光谱诊断方法。其创新之处体现在，一、建立了有普适性的碰撞辐射模型，能准确地预言多种低温等离子体设备的放电状态和发射光谱。本文的模型在气压从0.1 Pa到大气压，电离率从10-6到10-3的很宽的放电条件范围内都能给出与发射光谱测量实验一致的结果。二、新提出的光谱诊断方法能够适用于各种低温等离子体设备。尤其是对工业领域的许多放电设备而言，其他诊断方法由于射频干扰强、电离率低等原因而不能使用，但本文提出的方法仍能够有效地测量电子温度和密度。三、提出了一些新概念。本文提出的“特征电子密度”和“化学动力学区域”可以将等离子体的宏观控制参数和微观粒子的动力学过程直观地联系起来。由此可以清晰地描述各种低温等离子体的碰撞辐射机理的区别和联系。 通过光谱实验和碰撞辐射模型，本文系统地分析了低温等离子体中氩原子2p能级的粒子数分布规律，首次指出了大气压低温等离子体中以2p2、2p6、2p10能级密度较高为特征的非平衡粒子数分布。利用本文的发射光谱诊断方法，我们还给出了容性耦合等离子体和大气压下微波激发的微等离子体中电子密度随驱动频率、放电功率和放电间隙宽度等参数的变化规律。通过将新的光谱诊断方法与空间分辨测量技术相结合，本文还首次指出了大气压微等离子体中高能电子和低能电子具有不同的空间密度分布。
Optical emission spectroscopy (OES) is one of the most important and simple diagnostic tools in plasma physics. It is a non-invasive method and is not affected by the rf fields or magnetic fields. However, it needs a collisional-radiative model (CR model) to interpret the emission spectra. The development of this model, which describes the dominant collisional and radiative processes of excited particles correctly, along with new optical diagnostic techniques, are the purpose of this work. A large variety of low-temperature plasmas are investigated by using the optical and other diagnostic tools and the CR model. By comparing their results, the simple CR models for argon and nitrogen plasmas are developed, as well as several new diagnostic techniques based on OES. The differences between this work and the previous ones are as follows:1.The new CR models can predict the discharge state and emission spectra correctly, for a wide variety of discharges and over a wide parameter range.2.The new optical techniques can be used to obtain the electron temperature and density under strong rf field or with low ionization ratio, suitable for many industrial discharges, in which other diagnostic methods do not work.3.Some new concepts, including the characteristic electron density and the kinetic regime for an excited level, are proposed and used to describe the transition of the important processes with the discharge parameters. The nonequilibrium population distribution of argon 2p levels is investigated by using the OES and the simple models. The electron densities in the capacitively coupled plasmas and the microwave microplasmas are measured. The difference in distribution pattern between the high- and low-energy electrons in the microplasmas is given by using a spatially-resolved optical system.
