Helium is frequently used as a working medium for the generation of plasmas and is capable of energetic photon emissions. These energetic photon emissions are often attributed to the formation of helium excimer and subsequent photon emission. When the plasma device is exposed to another gas, such as nitrogen, this energetic photon emission can cause photoionization and further ionization wave penetration into the additional gas. Often ignored are the helium resonance emissions that are assumed to be radiation trapped and therefore not pertinent to photoionization. Here, experimental evidence for the presence of helium atomic emission in a pulsed discharge at ten’s of Torr is shown. Simulations of a discharge in similar conditions agree with the experimental measurements. In this context, the role of atomic and molecular helium light emission on photoionization of molecular nitrogen in an ionization wave is studied using a kinetic modeling approach that accounts for radiation dynamics in a developing low-temperature plasma. Three different mixtures of helium at a total pressure of 250 Torr are studied in simulation. Photoionization of the nitrogen molecule by vacuum ultraviolet helium emission is used as the only seed source ahead of the ionization front. It is found that even though radiation trapped, the atomic helium emission lines are the significant source of photoionization of nitrogen. The significant effect of radiation trapped photon emission on ionization wave dynamics demonstrates the need to consider these radiation dynamics in plasma reactors where self-absorbed radiation is ignored.

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氦和氦/氮混合物中真空紫外发射的研究

氦气经常用作产生等离子体的工作介质，并且能够发射高能的光子。这些高能光子发射通常归因于氦准分子的形成和随后的光子发射。当等离子体装置暴露于另一种气体（例如氮气）时，这种高能光子发射会引起光电离，并进一步使电离波渗透到其他气体中。通常被忽略的是氦共振发射，这些发射被认为是被辐射捕获的，因此与光电离无关。在此，显示了在Tors十点的脉冲放电中存在氦原子发射的实验证据。在类似条件下的放电模拟与实验测量结果一致。在这种情况下，使用动力学建模方法研究了原子和分子氦发光对电离波中分子氮的光电离的作用，该方法考虑了正在发展的低温等离子体中的辐射动力学。在模拟中研究了三种总压力为250 Torr的氦气混合物。通过真空紫外氦气发射使氮分子发生光电离，被用作电离前沿之前的唯一种子源。发现即使捕获了辐射，原子氦发射线也是氮光电离的重要来源。辐射俘获的光子发射对电离波动力学的重大影响表明需要在忽略自吸收辐射的等离子体反应器中考虑这些辐射动力学。