甲醇交流放电产物的光谱研究

Study on Decomposition Products of Methanol in AC Discharge by Spectroscopy

利用浓度调制光谱技术测量甲醇交流放电分解产物的发射光谱,在300～700nm之间主要观测到激发态CO分子的B^1Σ^＋—A^1Π Angstrom跃迁带、激发态CH分子430nm附近的A^2Δ—X^2Π跃迁带系和390nm附近的B^2Σ^-—X^2Π跃迁带系以及CHO（329.82nm）,CH2O（369.8nm）,CH3O（347.8nm）,H（巴末耳线系）的发射谱线。通过光谱强度分析得到,CO激发态B^1Σ^＋的振动温度达1638K,CH激发态A^2Δ的振动和转动温度分别为4200和1100K。改变放电电压和样品气压,测量CO,CH和H的发射光谱强度的变化关系,发现增加放电电压或减少样品气压,CO（B^1Σ^＋）和H（656nm）的发射光谱强度比CH（A2Δ）发射光谱强度增加得快,从而进一步讨论了甲醇交流放电解离通道和产氢机制。

The intermediate decomposition products of methanol （CH3OH） in an AC discharge were diagnosticated via concentration modulation spectroscopy. Several main vibrational bands of CO Angstrom B^1Σ^＋-A^1Π system, CH A^△2-X^2Π system at 430 nm and B^2Σ^--X^2Π at 390 nm, as well as CHO（329.82 nm）, CH2O（369.8 nm）, CH3O（347.8 nm） and Balmer series spectra of H atom were identified in the region between 300 and 670 nm. Furthermore, the dependences of the emission spectral intensities of the intermediate decomposition products on the discharge voltage and parent gas pressure were investigated in detail. The experiments indicated that the relative population ratio of CO（B^1Σ^＋） and H increases with increasing discharge voltage more quickly than that of CH（A^2△）. Several possible reaction passages were given and discussed. Additionally, the vibrational and rotational temperatures of CH（A^2△） were determined to be about 4 200 and 1 100 K respectively, and the vibrational temperatures of CO（B^1Σ^＋） were determined to be about 2 500 K by analyzing the intensity distribution using LIFEBASE computer program. The decomposition mechanism of methanol in the discharge plasma was discussed as well.