Formation and Excitation of CN Molecules in He–CO–N2–O2 Discharge Plasmas

Abstract

The emission by electronically excited CN molecules is a prominent feature in the spectrum of active nitrogen containing traces of carbonaceous species. A large amount of experimental work has been devoted to an investigation of CN emission. However, up to now the plasma chemistry of CN radicals and processes leading to the excitation of CN electronic states are still poorly understood. The results of experimental measurements and numerical simulations are compared in order to establish the role of various channels of CN creation in the ground and excited states.

Influence of nitrogen on thermodynamic properties and plasma composition in discharge tube of CO-laser

“…It can be seen that the measured and calculated values agree very well. Plasma-chemical processes determining CN concentration are described in [9] in detail. It was found that the CN molecules under conditions characteristic for discharge plasma of CO lasers are produced in processes…”

“…Experimental set-up has been described already in a previous work [9]. The water-cooled discharge tube from molybdenum glass, 17 mm in diameter, was used in the experiment.…”

“…The method is based on knowledge of population of electrically excited states, which under experimental conditions applied here are excited mainly by direct collision from ground state and decay in radiation processes. Thus concentration of carbon in ground state can be determined from the simple balance equation: The population of CN in ground state was calculated from absorption spectra [9]. We have employed the method of two identical light sources.…”

“…The concentrations of CN molecules have been measured in flowing He = CO − N 2 discharges [6][7][8] and in sealed-off systems, and theoretically determined based on a model of plasma-chemical processes -see [9]. Unfortunately, dependence of other plasma-chemical products in CO-laser medium on experimental conditions were not studied.…”

Near-infrared wavelength calibration of astrophysical spectrographs with the emission spectrum of the CN molecule

“…21 The chemical processes that take place inside the discharge are still an active field of research: probable reaction chains for the formation and excitation of the CN molecule in a He-CO-N 2 -O 2 discharge plasma have been described in the literature, but "up to now the plasma chemistry of CN radicals and processes leading to the excitation of CN electronic states are still poorly understood". 22 …”