Diffusion of Excited Neutral Particles: Basic Studies and Potential Applications

Abstract

Recent experiments, carried out in highly pure samples of molecular nitrogen, have demonstrated the strong influence exerted by neutral, excited metastable states. The influence of the electronically excited, metastable N2(A) state on the ionisation growth is demonstrated through observation of the diffusion phenomena associated with the spatial and temporal growth of ionisation. Evidence has also emerged demonstrating the existence of a second metastable particle influence. The diffusion time observed, however, is not consistent with it being due entirely to an electronically excited state such as the metastable N2(a′) state. Rather the observations suggest the possibility that intersystem crossings between the N2(a′), the highly vibrationally excited N2(X) states and the N2(A) state may be responsible for the increased diffusion time and large molecular size. The possible relevance of these findings to applications such as plasma nitriding is canvassed.