高气压直流辉光CH_4/H_2等离子体的气相过程诊断

A diagnosis of gas-phase processes in a high pressure DC CH_4 /H_2 plasma

对高气压(约100Torr)直流辉光碳氢等离子体的气相过程进行了光谱和质谱原位诊断.在高气压下,等离子体不同区域光发射特性存在明显差异.正柱区存在着以C2和CH为主的多个带状谱和分立谱线,阳极区粒子发射谱线明显减少,而在阴极区则出现大量复杂的光谱成分,表明高气压情形下等离子体与阴极间强烈的相互作用将导致复杂的原子分子过程.从低气压到高气压演变过程中,电子激发温度降低而气体分子转动温度升高.在高气压下,高甲烷浓度导致C2,C2H2及C2H4增多而C2H6减少.表明在高气压条件下,气体温度对气相过程的影响作用显著增强.

In this work, gas phase processes in a high pressure （-100 Torr） DC hydrocarbon plasma are investigated in situ by optical emission spectroscopy and mass spectroscopy. In the high pressure plasma, optical emission characteristics of glow layers are obviously different. C2, CH dominated band spectra and discrete spectra are distinctively observed in the positive column, whereas the emission intensity is found to decrease in the anode region. In the cathode region, a large number of complicated spectra are detected, which indicates the intensive interaction between the cathode and plasma under high pressure induces complicated atomic and molecular processes. With the the increase of pressure, electron excitation temperature decreases while gas rotational temperature goes up. High methane concentration causes increases in C2, C2H2 and C2H4 but a reduction in C2H6. Those suggest that the effect of gas temperature. on gas phase process is significantly enhanced under high pressure.