脉冲流光放电激发解离H_2O分子的动力学过程

Excited Dissociation Kinetics of H_2O by Pulsed Streamer Discharge

采用色散荧光光谱、时间分辨光谱和空间分辨光谱方法,在标准大气压(1.013×105Pa)下,对以N2气为载气的H2O蒸气脉冲流光放电等离子体激发解离反应动力学过程进行了实验研究.将所得色散荧光谱归属于N2(C3Πu→B3Πg)、·OH(A2Σ+→X2Π)、H(n=3→n=2)的辐射跃迁;并对N2*、·OH*、H*三种活性粒子的指纹灵敏谱线(337.2、308.4、656.5nm)荧光信号进行了时间分辨测量.结果表明,·OH*和H*荧光信号分别滞后N2*荧光信号7.4ns和17.6ns,由此推断H2O分子的激发解离通道为:H2O分子与高能电子发生非弹性碰撞激发,被激发到第一激发电子态的高振动能级,然后自解离成激发态的·OH*自由基和基态的H原子.空间分辨测量结果表明,在距负电极0.5mm附近,活性荧光粒子浓度最高,正好对应流光放电的负辉区,该区域电子温度和电子浓度最高,更有利于活性粒子的产生.

The methods of the disperse fluorescence, temporal-resolved spectrum and spatial-resolved spectrum were used to study the excited dissociation kinetics of N2/H2O gas in the pulsed streamer discharge plasma at the standared atmospheric pressure （1.013×10^5 Pa）. The main spectra detected in the experiment are assigned to C^3IIu→B^3IIg for N2, A^2∑^＋→X^2II for · OH radical, and （n=3→n=2） for H atom, respectively. The temporal-resolved measurements at 337.2, 308.4, 656.5 nm showed that the occurrences of ·OH^＊ and H^＊ were 7.4 ns and 17.6 ns later than that of N2^＊ respectively. So the dissociation process of H2Ocan be described as that H2O is excited to high vibrational level of the first excited state by non-elasticity collision with electron, and then dissociates to ·OH^＊ radical at excited state and H atom at ground state. Furthermore, spatial-resolved measurements showed that the densities of active particles reached the maximum at 0.5 mm away from negative electrode corresponding to the negative glow region of streamer discharge, where the maxima of electron temperature and density were helpful to the formation of these active particles.