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arXiv 2303.01883physics.plasm-ph
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通过电学测量及中性和离子质谱法表征 $N_2-H_2$ 直流辉光放电

Characterization of a DC glow discharge in $N_2-H_2$ with electrical measurements and neutral and ion mass spectrometry

Audrey Chatain, Ana Sofia Morillo-Candas, Ludovic Vettier, Nathalie Carrasco, Guy Cernogora, Olivier Guaitella

AI总结:

本研究通过电学测量和质谱法表征了低气压下N₂-H₂直流辉光放电,发现少量H₂显著影响等离子体特性并生成含氢离子,为泰坦电离层活性物种提供参考。

摘要:

在低气压(约1 mbar)和低功率(0.05至0.2 $W.cm^{-3}$)条件下,研究了在 $N_2$ 直流辉光放电中添加少量 $H_2$ 的影响。我们定量测量了当 $H_2$ 添加量在0至5%之间变化、气压在0.5至4 mbar之间变化以及电流在10至40 mA之间变化时的电场、电子密度、氨生成量以及正离子的形成。添加少于1%的 $H_2$ 对 $N_2$ 等离子体放电有显著影响。氢会猝灭 $N_2$ 的(较高)振动能级及其一些高能亚稳态。这导致放电电场增强,进而使平均电子能量增加。因此,推测会产生更多的自由基和激发态物种。氢的添加还导致新物种的形成。特别是,观察到了氨和含氢离子,其中主要的是 $N_2H^+$ 和 $NH_4^+$,此外还有 $H_3^+$、$NH^+$、$NH_2^+$、$NH_3^+$、$N_3H^+$ 和 $N_3H_3^+$。与类似实验条件下的射频电容耦合等离子体(RF CCP)放电相比,两种放电产生了相似的观测结果。因此,在适当的电离条件下对实验室中的 $N_2-H_2$ 放电进行研究,可以为泰坦电离层中可能存在的由氮和氢组成的等离子体物种提供一些见解。在这里,我们识别出了一些质子化离子,它们是可能参与泰坦有机气溶胶侵蚀的活性物种。

英文摘要:

The addition of small amounts of $H_2$ were investigated in a DC glow discharge in $N_2$, at low pressure (~1 mbar) and low power (0.05 to 0.2 $W.cm^{-3}$). We quantified the electric field, the electron density, the ammonia production and the formation of positive ions for amounts of $H_2$ varying between 0 and 5%, pressure values between 0.5 and 4 mbar, and currents between 10 and 40 mA. The addition of less than 1% $H_2$ has a strong effect on the $N_2$ plasma discharges. Hydrogen quenches the (higher) vibrational levels of $N_2$ and some of its highly energetic metastable states. This leads to the increase of the discharge electric field and consequently of the average electron energy. As a result, higher quantities of radical and excited species are suspected to be produced. The addition of hydrogen also leads to the formation of new species. In particular, ammonia and hydrogen-bearing ions have been observed: $N_2H^+$ and $NH_4^+$ being the major ones, and also $H_3^+$, $NH^+$, $NH_2^+$, $NH_3^+$, $N_3H^+$ and $N_3H_3^+$. The comparison to a radiofrequency capacitively coupled plasma (RF CCP) discharge in similar experimental conditions shows that both discharges led to similar observations. The study of $N_2-H_2$ discharges in the laboratory in the adequate ionization conditions then gives some insights on which plasma species made of nitrogen and hydrogen could be present in the ionosphere of Titan. Here, we identified some protonated ions, which are reactive species that could participate to the erosion of organic aerosols on Titan.

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