On determination of the degree of dissociation of hydrogen in non-equilibrium plasmas by means of emission spectroscopy: II. Experimental verification

Abstract

The method of spectroscopic determination of the degree of dissociation of hydrogen in non-equilibrium plasma, proposed in our previous paper, was verified under various plasma conditions. Three different gas discharges have been used, namely: (i) a DC-arc discharge, (ii) an RF discharge, f = 200 kHz and (iii) an MW discharge, f = 2.45 GHz, under pressure p = 0.3–8 mbar. Relative intensities of atomic and molecular spectroscopic lines, the Hα and Hβ line and the (2-2)Q1 line of the Fulcher-α system, and the gas temperature were measured in a wide range of discharge conditions and used for the determination of the degree of dissociation of hydrogen. It is shown that the method leads to plausible results in the whole range of discharge conditions studied in this paper. In particular, for the first time an influence of the redistribution of the population density of excited hydrogen atoms among fine structure sublevels on values of the degree of dissociation of hydrogen obtained by the method was investigated experimentally. It is also shown, that the influence is rather significant. The assumption of Boltzmann populations of the sublevels is more appropriate than neglecting the redistribution after electron impact excitation for p > 1 mbar.