Two-dimensional space-time-resolved emission spectroscopy on atmospheric pressure glows in helium with impurities

The time dependence of the spectral emission of an atmospheric pressure glow discharge in helium with impurities has been studied with a two-dimensional spatial resolution. Emissions from He I (3s(3)S-->2p(3)P:lambda=706.5 nm) and N-2(C(3)Pi(u)-->B(3)Pi(g):lambda=337.1 nm) are used to qualitatively map the distributions of high- and low-energy electrons, respectively. The emission from N-2(+)(B(2)Sigma(u)(+)-->X(2)Sigma(g)(+):lambda=391.4 nm) provides qualitative information about the relative spatial distribution of He-* metastable atoms within the discharge gap. The results demonstrate a radial spreading of the discharge during the current pulse as well as the formation of a ringlike, radially propagating cathode layer late in the current pulse. (C) 2004 American Institute of Physics.