Lukáš Schmiedt

Study of properties of CO2 laser mixture

The positive column of DC glow discharge sustained in CO2 mixture (containing CO2, N2 and He) has been studied in pressure range (300÷1400) Pa and for discharge currents up to 40 mA. Parameters of discharge — electrical field strength and emission spectra — have been studied by means of double-probe method and optical emission spectroscopy. Optical scanner of original construction that enables us to study radial variations of intensities of emission lines and bands has been used for the collection of emission spectra. We have focused on the investigation of intensities of spectral bands of the second positive system of molecular nitrogen corresponding to the transition N2(C)→N2(B) in the presented paper. It has been found that shapes of radial profiles of studied bands are independent on pressure and discharge current, despite the fact that intensity of N2(C) bands decreases with increasing pressure and with decreasing current. It has also been possible to estimate vibrational temperatureTvib from measured intensities of N2(C) bands. It was observed thatTvib stays almost constant in the radial direction under our experimental conditions, but it increases with increasing discharge current and slightly decreases with increasing pressure.

T- and H- forms of dc oxygen discharge at medium pressures: spectroscopic study

Abstract The active DC glow discharge sustained in the pure oxygen can be employed in various technological applications, such as thin layer deposition or sterilization. Considering applied pressures of hundreds of Pascals, two different forms of the positive column of the discharge can co-exist: T- and H-form. These forms are commonly distinguished according to the values of the axial electric field strength: values in the H-form are generally one order of magnitude higher compared to the T-form. However, electric measurement itself may often affect the discharge plasma. Optical emission spectroscopy as a non-invasive diagnostic was therefore employed as an alternate characterization of both forms. We found that the H- and T-forms can be clearly recognized by values of intensities of particular oxygen spectral lines. This characterization enabled us to observe transition between the both particular forms when spatial distribution measurements were employed. Moreover, transition in the rotational temperature Trot was also observed. Graphical Abstract

Properties of T and H forms of DC glow oxygen discharge sustained at medium pressures up to 1000 Pa

Summary form only given. The DC glow discharge in oxygen and its mixtures can be utilized in many applications (e.g. plasma etching, sterilization, thin layer deposition or treatment). Oxygen plasma is therefore subject of both numerical and experimental studies. One of the important discharge parameters is the kinetic temperature of the neutral particles which often governs rate constants of various processes such as dissociation or diffusion. Considering the case of oxygen, the kinetic temperature can be simply obtained by its comparison with rotational temperature T rot determined from emission spectra of the oxygen molecule1.