Spatially resolved, absolute densities of atomic oxygen are measured for several helium-based admixtures in the effluent of the COST Reference Microplasma Jet using two-photon absorption laser induced fluorescence (TALIF). Admixtures investigated include a helium-only admixture, four helium/oxygen admixtures (0.1, 0.5, 0.6, and 1.0 oxygen), and a helium/water admixture (2500 ppm water), chosen to coincide with previously published characterizations of plasma-treated liquid. The atomic oxygen TALIF signal is calibrated for density using the noble gas xenon, which possesses a very similar two-photon excitation and fluorescence scheme. Measurements are conducted for the jet operating in ambient air with both an open effluent and a liquid surface present, allowing for comparison with liquid phase measurements conducted under similar conditions. The presence of a water surface does not appear to alter the background chemistry in the effluent but reduces O densities close to the liquid interface when compared to a similar distance from the nozzle in an open effluent case. This may be the result of a reduction in flow velocity caused by the liquid obstructing the gas flow. Additionally, measurements near the liquid surface revealed a region of atomic oxygen well outside of where the core of the effluent impinges on the liquid. This is likely relevant for applications as it considerably expands the surface area subject to O absorption. Critically, in situ measurements of the effective lifetimes of the laser-excited 3p³P_J state of atomic oxygen were recorded in the effluent by employing a picosecond (ps) laser and a nanosecond (ns) ICCD. By experimentally determining the contribution from collisional quenching via the in situ effective lifetime measurements, significant improvements in the accuracy of the atomic oxygen density calibration were made, with differences of approximately 30 from existing methods of estimating quenching rates at atmospheric pressure. Finally, spatially resolved atomic oxygen densities allow for an investigation of O formation and extinction pathways in the effluent and a comparison between admixtures.

使用双光子吸收激光诱导荧光 (TALIF) 测量 COST 参考微等离子体射流流出物中几种氦基混合物的原子氧的空间分辨绝对密度。外加剂研究包括仅氦混合物，四氦/氧外加剂（0.1 ，0.5 ，0.6和1.0氧气）和氦/水混合物（2500 ppm 水），选择与先前公布的等离子体处理液体的特征相吻合。使用惰性气体氙气校准原子氧 TALIF 信号的密度，氙气具有非常相似的双光子激发和荧光方案。测量是针对在环境空气中运行的射流进行的，同时存在开放的流出物和液体表面，从而可以与在类似条件下进行的液相测量进行比较。水表面的存在似乎不会改变流出物中的背景化学，但与在开放流出物情况下与喷嘴的相似距离相比，会降低靠近液体界面的 O 密度。这可能是由于液体阻碍气流而导致流速降低的结果。此外，液体表面附近的测量结果显示，在流出物核心撞击液体的位置之外，有一个原子氧区域。这可能与应用有关，因为它大大扩展了受 O 吸收的表面积。关键的是，通过使用皮秒 (ps) 激光和纳秒 (ns) ICCD，在流出物中记录了激光激发的 3p ³ P _J原子态氧的有效寿命的原位测量值。通过原位有效寿命测量实验确定碰撞淬火的贡献，原子氧密度校准的准确性得到了显着提高，与现有的估计大气压淬火速率的方法相差约 30 。最后，空间分辨的原子氧密度允许研究流出物中 O 的形成和消亡途径以及混合物之间的比较。