Measure of atomic nitrogen concentration in the nitrogen post-discharge

Clean post-discharge nitrogen plasma and nitrogen plasma with different traces have been focus of scientists for more than 50 years and there were published many articles on theme active discharge, post-discharge, processes and reactions. It is possible to create kinetic models from all these information and then calculate concentrations of elements in atomic form. This diploma thesis is focused on measuring of concentration of atomic nitrogen for different conditions (decay time, pressure, admixture). The titration method by nitric oxide in post-discharge was used to determinate of concentration of atomic nitrogen. All experimental results were obtained by the optical emission spectroscopy. Optical emission spectra were taken in the range of 300-600 nm. DC discharge was created in a quartz tube in a flowing regime. The flowing regime was chosen for this experiment because of better time resolution of decay time, order in milliseconds. Decay time was in the range of 16 – 82 ms for individual experiments. Nitrogen flow was 400 mln/min. Nitrogen oxide flow was in the range of 0-10 mln/min and it was added at the selected post-discharge time. Trace of methane was 0,006 % of the whole volume. Total gas pressure was set on values from 500 to 4000 Pa. The output of discharge was set on constant value of current 150 mA and the output has changed according to the amount of pressure. Nitrogen first positive, second positive and first negative spectral systems, NO spectral system and NO2* spectral system were recognized in all measured spectra. Absolute concentration of atomic nitrogen was specified by the method of titration of NO. Traces of methane increase dissociation of molecular nitrogen and therefore increase the concentration of atomic nitrogen. This thesis brings new results into longtime research of moon Titan and new results into study of processes in nitrogen-methane plasma