In low pressure low temperature plasmas (p ~ Pa, T e ~ eV) the upper levels of the Balmer series of the hydrogen atom are populated by several excitation channels. While electron impact excitation is dominant for so-called ionizing plasmas (T e → 10 eV), dissociative recombination (DR) via the molecular ion becomes dominant in so-called recombining plasmas (T e → 1 eV). In the intermediate range, several other channels may be relevant as well. The expansion region of an ECR discharge, which represents such a plasma, is analyzed regarding the composition of the excitation processes as well as the line profiles of the Balmer series (for H α to H δ ). Significantly broadened line profiles compared to Doppler broadening of thermal hydrogen atoms are revealed. The resulting line profiles resemble two Gaussian components with distinct FWHM (narrow component close to apparatus profile: ≈25–30 pm; broad component: ≈50–100 pm), where the broad part contributes to 10%–40% to the emissivity, depending on the individual Balmer line and the plasma conditions. Collisional radiative modeling was applied in order to determine the contributions of the different excitation channels. It turned out that for each of the lines of the Balmer series, population via DR contributes to the total excitation with a similar share as the share of the broad component of the line profile. Hence, it is concluded that DR is responsible for the broad component in the Balmer line profiles. The implication of this analysis on the spectroscopic determination of the atomic hydrogen density using a simple line ratio method (H γ /Fulcher) is illustrated.

中文翻译：

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解离重组及其对氢巴尔默系列谱线的影响

在低压低温等离子体 (p ~ Pa, Te ~ eV) 中，氢原子的 Balmer 系列的上能级由几个激发通道构成。虽然电子碰撞激发在所谓的电离等离子体 (T e → 10 eV) 中占主导地位，但通过分子离子的解离复合 (DR) 在所谓的复合等离子体 (T e → 1 eV) 中占主导地位。在中间范围内，其他几个通道也可能相关。ECR 放电的扩展区域（代表这种等离子体）根据激发​​过程的组成以及 Balmer 系列的线轮廓（对于 H α 到 H δ ）进行分析。与热氢原子的多普勒展宽相比，显着展宽的线轮廓被揭示。由此产生的线轮廓类似于具有不同 FWHM 的两个高斯分量（靠近仪器轮廓的窄分量：≈25-30 pm；宽分量：≈50-100 pm），其中宽部分对发射率的贡献为 10%-40%，取决于各个 Balmer 生产线和等离子体条件。应用碰撞辐射建模以确定不同激发通道的贡献。结果表明，对于 Balmer 系列的每条线，通过 DR 的填充对总激励的贡献与线轮廓的宽分量的份额相似。因此，得出的结论是 DR 对 Balmer 线型材中的广泛成分负责。