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Study of laser mixture in the large pressure region
Morávek, Matěj Jan ; Hrachová, Věra (advisor) ; Kudrna, Pavel (referee)
This work studies discharge plasma in a mixture of gases, similar to that used in the so-called CO2-lasers. This mixture consists of CO2, N2 and He. The effect of the mixture composition and discharge parameters (especially pressure, in the range of 266 Pa - 100 kPa) on the distribution of energy in the vibrational levels of nitrogen was examined. This is important parameter for modelling of the discharge plasma. The effect of the mixture composition on the degree of dissociation of the CO2 molecules was also studied. The relative concentration of CO was applied to find the conditions leading to a minimal dissociation of the carbon dioxide. Measurements of radial profiles were also made. Results from two discharge tubes made from different materials were compared. Two types of discharge were utilized to acquire a wide pressure range - low pressure DC glow discharge in the range of 266 Pa to 1330 Pa and dielectric barrier discharge in the range of 5 kPa to 100 kPa. Both discharges are used in commercial CO2-lasers. We observed a descending dependence of the vibrational temperature on the pressure and a big step caused by increased occurrence of standing ionizing waves in the mixtures with low nitrogen ratio. Vibrational temperature in the DBD was markedly lower than in the DC GD, because of the...
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The Study of Transient Species and Precursors of Biomolecules using Spectroscopic Techniques
Ferus, Martin ; Civiš, Svatopluk (advisor) ; Šponerová, Judit E. (referee) ; Wild, Jan (referee)
The presented thesis is focused on a spectroscopic study of unstable radicals, ions and molecules in a positive column glow discharge and laser plasma. The research of these fragments is supplemented by a study of biomolecules formation from these species and influence of catalysts. Molecular dynamics of radicals, ions and unstable molecules has been studied using a time resolved Fourier transform infrared spectroscopy. Time resolved spectra of CH4, HCONH2, BrCN, CH3CN, CF3Br, (CF3)2CHBr positive column glow discharges have been measured and simulated using a kinetic model including molecular dynamics, collisions and chemical and radiation transfer processes. The model has been compared with our experimental results and time resolved spectra were described in details. Fit to a complex reaction mechanism has been used to estimate a rate constant of a HCN conversion to HNC by a collision with H radical. The study of precursors of biomolecules was focused on chemical consequences of a laser induced dielectric breakdown in formamide vapor and gaseous carbon monooxide with 18 O labeled water. Dissociation products have been detected using the Fourier transform absorption spectroscopy. The experimental results have been explained by a help of a chemical laser spark dynamics model. Additionally, our the...
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