微波等离子体中OH自由基的光腔衰荡光谱诊断

Characterization of OH Radicals in Microwave Plasma with Cavity Ring Down Spectroscopy

搭建了一套以可调谐半导体激光器为光源的连续波光腔衰荡光谱装置，将其与微波等离子体装置结合，对等离子体中的OH自由基进行了原位定量测量，同时考察了OH自由基数密度随气压和微波功率的变化情况。实验结果表明：以氮气为工作气体，在（O．66～3．99）×10^3Pa范围内，随着气压的升高，OH自由基数密度先增加后降低，在1．995×10^3Pa时达到最大值；随着微波功率的升高OH自由基数密度逐渐增加。

The dedicated setup for continuous wave cavity ring down spectroscopy （CRDS） ,with tunable diode laser as the ligth source, has been successfully developed to characterize in-situ the OH radicals in the microwave plasma. The influence of the pressure and microwave power on the number density of OH radicals was experimentally studied. The re- sults showed that the pressure and microwave power strongly affect the OH number density. For instance, as the nitrogen pressure, ranging from 0.66 ×10^3pa to 3.99 ×10^3pa, increases, the OH number density first increases, peaking at 1.995 ×10^3Pa,and then,decreases. We also found that the OH density increases with an increase of the microwave power.