Ionic species in atmospheric pressure plasma jets (APPJs) play an important role in plasma-surface and plasma-liquid interactions, nonetheless, they have not received the same attention as their neutral reactive species counterparts. In this work, a molecular beam mass spectrometer (MBMS) was used to characterize the ion compositions in the effluent of an APPJ operating in ambient air for different feed gases including Ar + O₂, Ar + air and Ar + H₂O mixtures inspired by gas compositions used for biomedical applications. Changes in compositions of positive and negative ions as a function of nozzle-to-substrate distance along the plasma plume were analyzed and compared with a pseudo-1D plug flow model. Positive and negative ions were detected up to distances of 12 mm from the visible plasma plume tip. The measurements enable to follow the ion conversion pathways in the effluent of the APPJs as a function of distance from the nozzle. The trends in ion yield obtained from a pseudo-1D plug flow model showed generally a good agreement with the experimentally observed trends after addition of ionic reactions to the previously reported reaction set but also some distinctive differences were observed. The dominant positive ions in the far effluent are water ion clusters, the most stable ion for all gas mixtures investigated, while a large variety of negative ions was found for different gas mixtures.

大气压等离子体射流 (APPJ) 中的离子物质在等离子体-表面和等离子体-液体相互作用中起着重要作用，然而，它们并没有像它们的中性活性物质对应物那样受到同样的关注。在这项工作中，分子束质谱仪 (MBMS) 用于表征在环境空气中运行的 APPJ 流出物中的离子组成，其中包括 Ar + O ₂、Ar + 空气和 Ar + H _{2 的}不同进料气体受用于生物医学应用的气体成分启发的 O 混合物。分析了正离子和负离子组成随等离子体羽流中喷嘴到基板距离的变化，并与伪一维活塞流模型进行了比较。在距可见等离子体羽流尖端 12 mm 的范围内检测到正离子和负离子。测量结果能够跟踪 APPJ 流出物中的离子转化路径，作为距喷嘴距离的函数。从伪一维活塞流模型中获得的离子产率趋势总体上与将离子反应添加到先前报告的反应组后实验观察到的趋势非常吻合，但也观察到了一些明显的差异。远流出物中主要的正离子是水离子簇，