低电压下氮气放电的发射光谱分析

建立了一套直流放电产生氮气等离子体装置，该装置以碳纳米管修饰ITO电极为阳极，铝平板为阴极，两极间距~80 μm。在室温低电压(低于150 V)对氮气进行气体放电，利用发射光谱法对氮气放电过程中的活性物种进行了诊断研究。在直流电压下，观测到氮气发射光谱中能量最强最清晰的谱带N₂(C3Π_u)，强度比较弱的Gaydon’s Green带系N₂(H₃Φ_u-G3Δ_g)，以及820 nm附近氮原子的发射谱线(4p-4p0)，发现氮分子的亚稳态是导致一系列激发态氮原子和氮气电离的主要因素，与交流电下(1.1 kV)产生的发射光谱相比，直流电下氮原子谱线光谱较强，且在500~800 nm范围检测到一个宽的分子谱带。考察了氧气与氢气对氮气发射光谱的影响，氧气对氮气的激发态有猝灭作用，使氮气发光强度降低，但其发射光谱图的谱型相似，都检测到氮气的第二正带系、Gaydon’s Green带系及氮原子谱线。当氮气与氢气的体积比为1∶1时，氮气的第二正带系及Gaydon’s Green带系都会受到很大的影响，说明加入的氢气可抑制氮等离子体激活，导致氮气的发光强度明显减弱，Gaydon’s Green System消失不见。碳纳米管修饰的ITO电极能使击穿电压降低，在10 V的低电压下，通过光电倍增管可观察到气体弱电离产生的光信号。

The Emission Spectroscopy of Nitrogen Discharge under Low Voltage at Room Temperature

A set of direct current(DC) discharge device of N₂ plasma was developed, carbon nanotubes(CNT) modified ITO electrode was used as anode, aluminum plate as cathode,with ~80 μm separation between them. Nitrogen emission spectra was observed at room temperature and low DC voltage (less than 150 V), and the emission spectrometry was used to diagnose the active species of the process of nitrogen discharge. Under DC discharge, the strongest energy band N₂(C3Π_u), the weak Gaydon’s Green system N₂(H3Φ_u-G3Δ_g) and the emission line of nitrogen atoms (4p-4p₀) at 820 nm were observed. Found that metastable state of nitrogen molecules were the main factors leadingto a series of excited state nitrogen atoms and nitrogen ionization. Compared the emission spectra under DC with that under alternating current (AC) (1.1 kV), andit can be seen that under DC the spectra band of nitrogen atoms can be obviously observed, and there was a molecular band in the range of 500～800 nm. The effect of oxygen and hydrogen on the emission spectra of nitrogen was investigated. The results showed that the oxygen inhibited the luminescence intensity of nitrogen, but the shape of spectra unchanged. All of the second positive system,Gaydon’s Green system and atomic lines of nitrogen can be observed. The second positive system and Gaydon’s Green system of nitrogen will be greatly affected when the volume ratio of nitrogen and hydrogen greatly affected is 1∶1, which was due to the hydrogen. The hydrogen can depresse nitrogen plasma activation, and make the Gaydon’s Green System disappeared. CNT modified ITO electrode can reduce the breakdown voltage, and the optical signal generated by the weakly ionized gas can be observed by the photomultiplier tube at low voltage of 10 V.