A. Kaňka

Spectroscopic Determination of Oxygen DC Glow-Discharge Temperature: Radial Profile of Gas Temperature

Rotational temperature in the oxygen DC glow discharge is determined from atmospheric A-band of molecular oxygen. Two methods of estimation of this parameter taking into account the quality of the detected spectra are analysed and compared. Radial profile of the rotational temperature is measured. No radial variations of rotational temperature have been observed in the positive column under our experimental conditions.

Study of the admixture influence on the oxygen spectra properties

Abstract The spectra of oxygen from two different producers and oxygen with small admixture of rare gases or nitrogen were studied. The spectra were generated by positive column of the glow discharge. The spectral lines (wavelength of 844.7 and 777.4 nm) and the bands of oxygen (atmospheric A-band of molecular oxygen and first negative system of molecular positive oxygen ion) were analyzed. It was found that in very pure oxygen (Linde production) the first negative system is practically not developed. Small admixture of another gas causes appearance of this system. The influence of the nitrogen was more significant. It is possible to conclude that existence or non-existence of the full first negative system is dependent on the presence of the admixture with energetic levels near to oxygen ones.

Study of Spectral Emission Behaviour in the Glow and Microwave Discharges of Oxygen

Because of the very important role of oxygen plasmas in various applications, both direct current and microwave discharges have been analysed from the point of view of emission spectra properties. In both cases silica discharge tubes with practically the same diameters were used. The following transitions of the oxygen discharges were studied: the atomic lines at 777.4 nm ( 5 P - 5 S) and 747.7 nm ( 3 D - 3 P 0 ), and the head at 759.4 nm of the atmospheric system (b 1 Σ + g , v = 0 - X 3 Σ - g , V = 0).

The discharge tube material influence on N2–O2 DC glow discharge

Abstract Plasma–wall interactions play an important role in kinetics of low-pressure discharges, since they can significantly influence plasma composition and consequently its properties. The main aim of submitted contribution is to investigate possible influence of different materials of discharge tubes on the properties of N 2 –O 2 DC glow discharge that is employed in a great number of technological applications. Two geometrically identical discharge tubes made from two different materials (Silica and Pyrex glass) have been used to this purpose. The positive column of the discharge in different N 2 –O 2 mixtures has been studied by means of optical emission spectroscopy and by probe measurements. It has been found that small admixture of nitrogen to oxygen discharge causes approximately twice higher increase of O atom spectral lines intensities in the case of Silica discharge tube compared to the Pyrex one. Other spectral bands as well as electrical field strengths have shown no significant distinctions in these two discharge tubes. The possibility of the estimation of O atom density by actinometry method has also been verified in the mixture.

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