Radiative Continuum of Molecular Hydrogen in a Diffuse Pulse-Periodic Discharge in Low-Pressure Humid Air

Abstract

Broadband radiative continuum of low-temperature plasma is observed upon excitation by various types of discharges and electron beams of inert gases, hydrogen, deuterium, their mixtures, and mixtures of inert gases with halogens. This work demonstrates experimentally that upon excitation of humid air by a pulse-periodic streamer discharge with low specific powers, the plasma color changes from red, corresponding to the emission of 1⁺ nitrogen system, to white. This phenomenon was recorded with decreasing pressure and increasing discharge current density. It was found that a broadband continuum appears in the emission spectrum, which was attributed to \({{a}^{3}}\Sigma _{{\text{g}}}^{ + }\) → \({{b}^{3}}\Sigma _{{\text{u}}}^{ + }\) electronic transitions between bound and repulsive terms of molecular hydrogen. We present data on the influence of the relative air humidity, voltage pulse duration, and discharge current density on the emission spectra and color of plasma radiation. The kinetic processes determining the mechanism of molecular and atomic hydrogen production under these conditions are analyzed.