光化线强度法研究大气压等离子体射流的氧原子浓度

Atomic oxygen concentration of an atmospheric pressure plasma jet investigated by actinometry

等离子体射流产生的众多活性粒子中,氧原子是化学活性非常强的氧化剂,也是生成其他含氧活性粒子的基础,因此确定氧原子浓度及其时空分布对提高等离子体射流的应用效率具有重要意义.针对于此,本工作利用单电极等离子体射流产生了实心结构的等离子体羽,利用高分辨光谱仪采集了放电的发射光谱.结果表明,等离子体羽中确实含有氧原子等活性粒子.采用光化线强度法通过比较氧原子谱线(777.4 nm)和氩原子谱线(750.4 nm)的强度比研究了等离子体中氧原子浓度.结果表明:等离子体羽中的氧原子浓度随着距离喷口距离的增加先减小后增大;固定其他实验参数的情况下,氧原子浓度随着外加电压峰值和工作气体流量的增加而增大;当工作气体中掺入空气后,等离子体羽中氧原子浓度随着空气体积分数的增加先增大后减小.结合放电机制,对以上实验现象进行了定性分析,所得结果对于大气压等离子体射流的应用具有重要意义.

Among the various active species produced in plasma jet,oxygen atom is a kind of oxidants with high chemical reactivity.Moreover,it is a fundamental specie to generate other reactive oxygen species.Therefore,it is very important for efficiency improvement in determining oxygen atom concentration in plasma jet.Aim to this status,a plasma plume with a solid morphology is generated downstream of a plasma jet in a single-electrode configuration.Optical emission spectrum is collected from the plasma jet by a high-resolution spectrometer,which presents that active species including oxygen atom are abundant in the plasma plume.Moreover,intensity ratio of O I(777.4 nm)and Ar I(750.4 nm)is investigated to obtain the variation of oxygen atom concentration by actinometry.Experimental results indicate that oxygen atom concentration in plasma plume first decreases and then increases with increasing distance from the jet nozzle.Furthermore,it increases with increasing peak value of applied voltage or gas flow rate.After mixing trace air into the working gas,it is found that oxygen atom concentration first increases and then decreases with increasing air content into the working gas.Optimal concentration of oxygen atom appears at about 0.02%air content.After considering discharge regime,the experimental phenomena mentioned above have been analyzed qualitatively.All these results are of great importance for the application of atmospheric pressure plasma jet.