Estimation of dissociation degree of N2 in an inductively coupled plasma by vacuum ultraviolet emission spectroscopy

A simple procedure for estimation of the N2 dissociation degrees in low-pressure, high-density plasmas is proposed. This procedure is applied to the estimation of the N2 dissociation in an N2 inductively coupled plasma and confirmed to give N2 dissociation degrees similar to those reported previously. The rf power and N2 pressure dependence of the N2 dissociation degree is also presented. The contribution of stepwise excitation out of N2 A3Σu+ [N2(A)] metastables to the N2 second positive emission is found to be negligible from the net excitation rate computed using an assumed cross section of the electron-impact excitation from N2(A) to the N2C3Πu state and the N2(A) number density deduced from a simple kinetic model. The recombination of N atoms on the inner surfaces of the plasma reactor used in this study is discussed briefly. Finally, the advantages of the N2 dissociation estimation by vacuum ultraviolet optical emission spectroscopy are mentioned.