Plasma-related studies in gas phase are challenging to carry out due to plasma’s transient and unpredictable behavior, excessive luminosity emission, 3D complexity and aggressive chemistry and physiochemical interactions that are easily affected by external probing. Laser-induced fluorescence is a robust technique for non-intrusive investigations of plasma-produced species. In this letter, we present 3D distributions of ground state hydroxyl radicals (OH) radicals in the vicinity of a glow-type gliding arc plasma. Such radical distributions are captured instantaneously in one single camera acquisition by combining structured laser illumination and a lock-in based imaging analysis method called FRAME. The interference of plasma emission is automatically subtracted by the FRAME technique. In addition, the orientation of the plasma discharge can be reconstructed from the 3D data matrix, which can then be used to calculate 2D distributions of ground state OH radicals in a plane perpendicular to the orientation of the plasma channel. Our results indicate that OH distributions around a gliding arc are strongly affected by gas dynamics. We believe that the ability to instantaneously capture 3D transient molecular distributions in a plasma discharge, with minimal plasma emission interference, will have a strong impact on the plasma community for in situ investigations of plasma-induced chemistry and physics.

由于等离子体的瞬态和不可预测的行为、过度的光度发射、3D 复杂性以及容易受到外部探测影响的侵蚀性化学和物理化学相互作用，气相中等离子体相关研究的开展具有挑战性。激光诱导荧光是一种用于非侵入式研究等离子体产生的物种的强大技术。在这封信中，我们展示了辉光型滑翔弧等离子体附近基态羟基自由基 (OH) 自由基的 3D 分布。通过将结构化激光照明和称为 FRAME 的基于锁定的成像分析方法相结合，可以在单个相机采集中即时捕获此类自由基分布。FRAME 技术会自动减去等离子体发射的干扰。此外，等离子体放电的方向可以从 3D 数据矩阵中重建，然后可以用来计算基态 OH 自由基在垂直于等离子体通道方向的平面中的 2D 分布。我们的结果表明，滑翔弧周围的 OH 分布受到气体动力学的强烈影响。我们相信，以最小的等离子体发射干扰即时捕获等离子体放电中 3D 瞬态分子分布的能力将对等离子体界产生重大影响等离子体诱导化学和物理的原位研究。