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

Abstract

AbstractThe 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.