Consequences of Photoelectron and Electric Field Emission on Propagation of Surface Ionization Waves

The propagation of atmospheric pressure surface ionization waves (SIWs) across dielectrics produce large fluxes of VUV radiation onto the surface. With non-planar topography, particularly with different materials, electric field enhancements adds to the already large electric field in the head of the SIW. Both VUV radiation and electric field enhancement can result in electron emission occurring ahead of the ionization front. With the range of VUV radiation being longer than the width of the SIW, surfaces can be preprocessed by photoelectron emission preceding the arrival of the SIW. A similar situation occurs with electric field emission. As the SIW approaches, for example, a triple point, the electric field at the triple point intensifies, which can lead to electric field emission prior to the arrival of the SIW.

Results will be discussed from modeling of propagation of SIWs across structured dielectric surfaces to investigate the consequences of photo-electron and electric field emission. These investigations were performed using the 2-dimensional model nonPDPSIM. Results will be discussed for SIWs sustained in air launched onto dielectric surfaces having micro-structure and rare-gas plasma jets incident onto micro-structured surfaces. We found that photoelectron emission can accelerate the propagation of SIWs due to seeding of electrons ahead of the ionization front, though this effect is sensitive to topography and other sources of electric field enhancement. The structure of the SIW is little affected by the increase in speed. The onset of electric field emission has significant effects on the propagation of SIWs while being sensitive to topography. The onset of electric field emission ahead of the ionization front can produce a reverse SIW, altering the propagation of the initial SIW.