High-Sensitivity In-Situ Diagnosis of NO_2 Production and Removal in DBD Using Cavity Ring-Down Spectroscopy

摘要

A highly-sensitive in-situ diagnosis approach for nitrogen dioxide(NO2) has been developed in dielectric barrier discharge(DBD) based on pulsed cavity ring-down spectroscopy(CRDS). Absorption bands of NO2in a spectral region from 508 nm to 509 nm were used,and a detection limit of 17.5 ppb was achieved. At this level of sensitivity,the quantitative and real-time monitoring of the production and removal of NO2are accomplished for the first time in the discharge region. By measuring the removal amount and rate at different NO2initial number densities from 1.54 × 1013cm-3to 2.79 × 1014cm-3,we determined the relationship between them and NO2initial number densities. The removal amount linearly increases with the initial number density,while the removal rate increases logarithmically. At a lower initial number density,the removal rate is limited. By considering the chemical kinetic mechanism in plasma,a qualitative explanation for the above phenomena is proposed:the additional NO2produced by discharge limits the removal rate,since the NO2concentration is dominated by the competition between the forward reactions(production) and the reverse reactions(removal).