E and H Modes of Inductively Coupled SO2 Plasma

Inductively coupled plasma (ICP) represents a source of charged as well as neutral reactive particles. Plasma created in sulfur dioxide (SO₂) gas is a source of SO radicals suitable for functionalization of delicate organic materials with SO groups, provided the appropriate discharge mode is chosen. The ICP was sustained in either Eor H-mode. In the first case, the plasma glow is rather uniform along the entire reactor and the color is dark blue due to extensive radiation originating from excited SO radicals. In the H-mode, the light intensity is orders of magnitude larger in the coil, and the image is white due to various atomic transitions in the entire spectrum. The plasma density in the H-mode is, therefore, large enough to cause not only dissociation of SO₂ to SO but also destruction of SO radicals to S and O atoms, so plasma created in H-mode is not that suitable for functionalization of organic materials with SO groups.