液相放电能够产生各种活性物质, 其中羟基自由基(OH), 氢自由基(H)被认为是引发液相化学反应的主要活性物种, 但由于其活性强寿命短的特点, 测量比较困难, 由于缺少标准样品, 定量测量更为困难。 用光学方法测量自由基是一种直接测量方法, 其特点是瞬时在线测量, 能立即获得数据, 进行时间和空间分布测量。 为了研究微波水中放电产生的自由基特性, 利用发射光谱诊断技术对微波水中放电产生的活性物质进行了在线检测, 考察了微波功率、 反应器内部压强对OH自由基相对光谱强度的影响, 并观测了等离子体中OH自由基强度的空间分布; 同时, 估算了微波液相等离子体中的电子激发温度。 实验结果表明, 微波水中放电可以产生大量的OH, H, O自由基, 其中OH自由基的相对光谱强度最强, 并随微波功率的增加呈现明显上升的趋势, 随反应器内部压强的增大而迅速减弱; 以OH为主的自由基主要产生于电极尖端附近。 微波液相等离子体的电子激发温度约为0.33×104 K。

A variety of active substances can be produced during discharge in liquid, in which hydroxyl radical (OH), hydrogen radical (H) is considered as main active species leading to liquid chemical reaction. However, it is difficult to measure them due to its characteristics of short activity and short life; especially it is more difficult to conduct quantitative measurement due to the lack of standard samples. In contrast to the indirect measurement of direct capture, the optical method of measuring free radicals is a direct measurement method, which is characterized by instantaneous on-line measurement that allows immediate data acquisition and time and spatial distribution measurements. In order to study the free radical properties of microwave discharge in water, the active substances produced by microwave discharge were investigated by optical emission spectroscopy. The effects of microwave power and internal pressure on the relative spectral intensities of OH radicals were investigated. The spatial distribution of OH radicals in the plasma was observed. At the same time, the electron excitation temperature was estimated. The experimental results showed that a large amount of OH, H, O radicals could be produced by microwave discharge in water, in which OH radicals had the strongest relative spectral intensity and showed a tendency to increase with the increase of microwave power; but were rapidly weakened with the increase of internal pressure. Free radicals based on OH radicals were mainly produced in the vicinity of the tip of the electrode. At the same time, the microwave excitation temperature of the microwave plasma in water was about 0.33×104 K.