大气压辉光放电的产生摆脱了真空装置的束缚, 且其中富含活性粒子, 因此大气压辉光放电在材料表面改性, 生物医学, 污染物处理等方面都具有良好的应用前景。 在其应用研究中, 含氧活性粒子如OH自由基和O原子等具有重要作用, 但目前关于氧原子浓度随工作气体中氧气含量的变化尚不清楚。 利用直流电压激励针-网放电装置, 以氩氧混合气体作为工作气体, 在去离子水中产生了弥散的大气压等离子体。 放电照片显示放电中包含明显的阳极辉区、 负辉区以及位于它们之间的正柱区, 这些特征区域的存在表明放电处于辉光放电机制。 光电测量结果表明, 气隙电压和发光信号随时间均是恒定的, 即放电是时间连续的无脉冲形式。 其中, 气隙电压随放电电流的增大先减小而后维持不变, 即放电的伏安特性曲线在小电流时具有负斜率, 在大电流时处于稳压阶段, 因此该水下放电在小电流时为亚辉光放电机制, 在大电流时为正常辉光放电机制。 通过采集250~900 nm范围内的放电发射光谱, 发现谱线主要集中在680~900 nm范围内, 这部分光谱由Ar Ⅰ和O Ⅰ(777.4和844.0 nm)组成。 此外, 还在波长308 nm处观测到微弱的OH谱线。 光谱测量结果发现, Ar Ⅰ(如750.4和763.5 nm)的谱线强度随工作气体中氧气含量的增加而单调地减小。 与之不同的是O Ⅰ的谱线强度随工作气体中氧气含量的增加先增大, 在氧气含量为1.5%时达到其最大值, 之后随氧气含量的增加而减小。 为了分析O Ⅰ的谱线强度随工作气体中氧气含量的变化关系, 通过光线化强度法（777.4 nm/750.4 nm）研究了氧原子浓度随工作气体中氧气含量的变化关系。 结果表明氧原子浓度随氧气含量的变化趋势与O Ⅰ谱线强度的变化趋势一致, 即随工作气体中氧气含量的增加表现为先增大后减小, 其最大值出现在氧气含量为1.5%时。 最后, 基于氧原子的产生机制和氧分子对电子的吸附作用对上述实验现象进行了定性的解释。 这些研究结果对于大气压辉光放电的应用具有重要意义。

Atmospheric pressure glow discharge (APGD) is abundant with active species, and a vacuum device is dispensable for APGD. Due to these good merits, APGD has extensive application prospects in material surface modification, biomedical application, pollutant treatment, and so on. In application research for APGD, oxygen-containing active species, such as OH radicals and O atoms, play an important role. Unfortunately, the influence of oxygen content in working gas on the concentration of the produced oxygen atom is not very clear up to now. Aim to this status, and a diffused atmospheric pressure plasma is excited by a direct-current voltage with a needle-mesh geometry, which is operated underwater of deionized water and with argon/oxygen mixture used as working gas. Discharge image presents three distinct regions, including anode glow, negative glow, and a positive column between them. The presence of these characteristic regions suggests that the discharge is operated in a glow discharge regime. By optical and electrical methods, results show that both gap voltage applied between the two electrodes and light emission signal is time-invariant, that is to say, the discharge operates in a continuous mode, other than the pulsed mode. Moreover, the voltage-current curve of discharge has a negative slope at low current and voltage stabilizing at high current, revealing that the discharge operated underwater is in a subnormal glow discharge regime at low current, and in a normal glow discharge regime at high current. By optical emission spectroscopy, spectrum collected in the range from 250 to 900 nm contains spectral lines mainly in the range of 680 to 900 nm, which are composed of Ar Ⅰ and O Ⅰ (777.4 and 844.0 nm). In addition, an OH line with weak intensity is also observed at 308 nm. With increasing O2 content of working gas, the intensity of Ar Ⅰ(750.4 and 763.5 nm) monotonously decreases. However, the intensity of O Ⅰ increases firstly, reaches a maximum with an oxygen content of 1.5%, then decreases with increasing O2 content. In order to analyze this phenomenon, the concentration of oxygen atom is then investigated as a function of oxygen content in working gas by using an intensity of O Ⅰ at 777.4 nm ratio to intensity of Ar Ⅰ at 750.4 nm. Results indicate that oxygen atom concentration with increasing oxygen content of working gas has a similar trend with O Ⅰ intensity, that is to say, oxygen atom concentration increases firstly and then decreases with increasing O2 content, and its maximum is reached with an oxygen content of 1.5%. Finally, a qualitative explanation is given through analyzing the generation process of oxygen atoms and the loss procedure of electrons attached by oxygen molecules. These results are of great significance for the application of APGD.