Molecular dissociation and vibrational excitation on a metal hot filament surface

The dissociation of diatomic molecules (H-2, N-2, O-2) on the surface of a metal hot filament (HF) has been studied theoretically, within the framework of a unified two-step reaction mechanism, and via joint experimental-modelling studies of the gas temperature and selected species concentration distributions in the vicinity of the HF. This approach allows description of the variations in atomic concentrations with distance (d, measured from the HF) as functions of HF temperature and gas pressure. Complications associated with the extension of such analyses to interpretations of prior experimental measurements for larger, heteronuclear molecules (CH4, nitrogen oxides) are discussed. The present analysis also provides a rationale for the d-dependent non-equilibrium [N-2(v = 1)]/[N-2(v = 0)] vibrational population ratios measured in tungsten HF-activated N-2 gas samples.