发表机构
Princeton Plasma Physics Laboratory, Princeton University（普林斯顿等离子体物理实验室，普林斯顿大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过空间分辨诊断揭示短辉光放电中甲烷解离与聚合的分离区域，并识别出超热氢原子及其对化学活化的贡献。
AI 中文摘要
本文对短直流辉光放电中甲烷分解化学进行了空间分辨映射，揭示了在400 mTorr的Ar-CH4混合物中解离与聚合的分离区域。采用激光诱导荧光（LIF）、双光子吸收激光诱导荧光（TALIF）和光学发射光谱（OES）技术，对氢原子（H）、亚甲基（CH）和双碳（C2）自由基的绝对数密度进行了成像。结果揭示了一个由非局域电子动力学驱动的分离化学环境。甲烷的初级解离局限于阴极鞘层（<4 mm），此处H原子密度达到峰值。对Hα谱线轮廓的分析识别出两个不同的超热H原子群体，其峰值动能分别约为110 eV和17.5 eV，分别归因于离子-表面反射和电子碰撞解离。次级自由基CH和C2的密度在距离阴极更远的鞘层-负辉光边界（y=4-6 mm）处达到峰值，将该区域确定为主要聚合区，其中C2峰值密度比CH高约370倍。放电在强非平衡条件下运行，这由低体相气体温度（约570 K）与发射CH(A)自由基的高振动温度（3300-4700 K）之间的差异所证实，后者作为特定高能解离激发路径的特征。这项工作展示了短辉光放电的结构化能量景观如何在空间上分离甲烷解离与后续聚合。动力学估算表明，超热H原子可能通过夺取反应在体相等离子体化学中发挥作用，预测的CH4活化速率超过热H群体的速率。
英文摘要
This work presents the spatially resolved mapping of methane decomposition chemistry in a short direct-current glow discharge, revealing segregated zones for dissociation and polymerization in an Ar-CH4 mixture at 400 mTorr. Laser-induced fluorescence (LIF), two-photon absorption LIF (TALIF), and optical emission spectroscopy (OES), are used to map the absolute number densities of atomic hydrogen (H), methylidyne (CH), and dicarbon (C2) radicals. The results reveal a segregated chemical environment driven by the non-local electron kinetics. The primary dissociation of methane is confined to the cathode sheath (< 4 mm), where the H atom density peaks at a value (). Analysis of the Halpha} line profile identifies two distinct suprathermal H atom populations with peak kinetic energies of ~110 eV and ~17.5 eV, attributed to ion-surface reflection and electron-impact dissociation, respectively. The densities of secondary radicals CH and C2 peak further from the cathode at the sheath-negative glow boundary (y=4-6 mm), identifying this region as the primary zone for polymerization, with the peak C2 density higher than that of CH by a factor of ~370. The discharge operates under strong non-equilibrium conditions, confirmed by the disparity between the low bulk gas temperature (~570 K) and the high vibrational temperature (3300-4700 K) of the emitting CH(A) radicals, the latter serving as a signature of a specific high-energy dissociative excitation pathway. This work demonstrates how the structured energy landscape of a short glow discharge spatially separates methane dissociation from subsequent polymerization. Kinetic estimates suggest that suprathermal H atoms may play a role in bulk plasma chemistry via abstraction reactions, with predicted CH4 activation rates exceeding those of the thermal H population.
Journal refShurik Yatom 2026 Plasma Sources Sci. Technol. 35 085024
