Validity of actinometry to measure N and H atom concentration in N2-H2 direct current glow discharges

Abstract

The validity of actinometry to measure N and H atoms in nitrogen-hydrogen direct current (dc) glow discharges was investigated. The experiments were conducted in positive columns of dc glow discharges, in mixtures of N2-xH2, where x varies from zero to one, pressures between 133.33 and 533.32 Pa and discharge currents from 1 to 50 mA. The electric fields were measured by electric probes (17 V cm-1<E<32 V cm-1), and the gas temperatures (490 K<Tg<910 K) were deduced from the rotational transitions of molecular-band systems. The actinometry was performed using argon as the actinometer gas and compared with laser induced fluorescence measurements of ground-state atoms, in order to establish the limits of the validity of actinometry. A theoretical approach was used in order to interpret the behaviour of the emission lines. In nitrogen-hydrogen positive columns, the actinometry method indicated the correct behaviour of the N atoms density in the range of zero to one for x and for H atoms in the region from x = 0 to x = 0.2.