OPTICAL EMISSION SPECTROSCOPY OF PULSED DC PLASMAS

Glow discharge -optical emission spectroscopy of different plasma gases such as H2, N2, N2-H2 and Ar-N2 generated by a cost effective 50 Hz pulsed-DC electrical power source is carried out to investigate the different excitation and ionization processes involved in the production of active species, for surface nitriding of materials. Spectroscopic study of hydrogen Balmer - line profiles are performed in an abnormal glow region of hydrogen plasma for investigating the dependencies of their line shapes and intensities on discharge parameters. A technique based on determining the relative intensities of neutral atomic hydrogen emission lines is used to evaluate the electron temperature whereas the electron density is extracted from Stark broadening ( FWHM ) of the H-beta emission profile . The plasma parameters are found to be strongly dependent on discharge conditions. The effect of inert gases such as Ar, He, etc on the production of active species is also investigated under different discharge conditions. The metastable states of these gases are found to be useful for enhancing the concentration of active species.