Measurement of the spatial distribution of metastable He in a pure He DC glow discharge with self-organized luminous patterns above the anode

We investigated the spatial distribution of metastable He atoms (He M ) in a pure He atmospheric-pressure DC glow discharge exhibiting self-organized luminous patterns above the anode. Laser-induced fluorescence (LIF) spectroscopy revealed the presence of He M not only in the positive column but also in the region above the anode surface. Since the estimated diffusion length of He M is shorter than 100 μm, the observed He M near the anode is considered to be produced locally rather than transported from the cathode region. A zero-dimensional reaction model including 29 reactions and 7 optical emission processes was constructed to examine possible reaction pathways involving metastable species, electrons, positive ions, and molecular He Rydberg states He 2 Ryd . The calculated HeM