Resolve the spatially varying methane density and electron energy distribution

Determine the spatially resolved methane density and full electron-energy distribution function throughout the short glow discharge to enable quantitative interpretation of the ratio between nascent excited hydrogen and thermally excited hydrogen populations.

Background

The Hα emission profile is decomposed into narrow, moderate, and broad components associated respectively with thermal hydrogen, electron-impact suprathermal hydrogen, and reflected suprathermal hydrogen. The authors use the ratio of the moderate- to narrow-component intensities as an indicator of the relative rates of nascent excited-hydrogen generation and excitation of thermal hydrogen.

A quantitative interpretation is not possible from the reported measurements alone because the methane density and the complete spatially varying electron-energy distribution are unavailable. These quantities are needed to determine the relevant production and excitation rates across the discharge gap.