Abstract

The results of a spectroscopic study of the conversion of acetylene and methane in a helium plasma jet produced by a direct current plasma torch are presented. The operating mode of the plasma torch corresponds to conditions that provide a high yield of carbon nanostructures. In the emission spectra recorded during the transverse observation of a 20-mm jet section following the outlet of the anode channel of the plasma torch, high-intensity Swan bands of the С₂ molecule are the dominant component in the visible wavelength range. The spectra show atomic hydrogen lines of the HI Balmer series from H_α to H_ε, numerous CI carbon lines from ultraviolet 247.9 nm to infrared 962–966 nm, and a number of HeI helium lines. The axial temperature values of the plasma jet were spectrally determined by the observed ionized carbon CII lines 283.7 nm, 392.0 and 426.7 nm. A joint analysis of the emission spectra and the mixture composition calculated in the Saha–Boltzmann approximation revealed the nature of the spatial heterogeneity of the studied He : C : H plasma jet. It is manifested by the difference in the electron temperature of the axial region of the jet, which is measured with ionized carbon lines CII (T_e(0) = 12 000–14 000 K) from the vibrational and rotational temperatures of C₂ molecules (T_V = T_R ≅ 5000 K) that emit intensely at the jet periphery. The electron density measured along the H_β and H_γ line widths, which varies in the range of the observed jet region of n_e = (4–2) × 10¹⁶ cm^–3, corresponds to the ionization equilibrium in a plasma He : C : H mixture with an electron temperature close to T_e measured by carbon-ion lines.

中文翻译：

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含碳氢化合物氦等离子体射流的光谱研究

摘要

提出了由直流等离子体炬产生的氦等离子体射流中乙炔和甲烷转化的光谱研究结果。等离子炬的操作模式对应于提供高产率的碳纳米结构的条件。在等离子炬的阳极通道的出口之后的20毫米喷射部的横向观察期间记录的发射光谱中，С的高强度天鹅带₂分子是在可见光波长范围内的主要组件。该光谱显示选自H的HI巴尔末一系列原子氢线_α至H _ε，从紫外线247.9 nm到红外线962–966 nm的大量CI碳谱线以及许多HeI氦谱线。通过观察到的电离碳CII线283.7 nm，392.0和426.7 nm，光谱确定了等离子流的轴向温度值。通过Saha–Boltzmann近似计算得出的发射光谱和混合物成分的联合分析揭示了所研究的He：C：H等离子体射流的空间异质性。它由射流轴向区域的电子温度差异表示，该温度是由C ₂分子的振动和旋转温度用离子化碳线CII（T _e（0）= 12 000–14 000 K）测量的（T _V = T _R≅5000 K）在喷流边缘强烈发射。沿_Hβ和_Hγ线宽度测量的电子密度在观察到的喷射区域n _e  =（4–2）×10 ¹⁶ cm ^–3的范围内变化，对应于等离子体He中的电离平衡：由碳离子线测得的电子温度接近T _e的C：H混合物。