T. Frentiu, M. Ponta, A. I. Mihaltan, E. Darvasi, M. Frentiu, E. Cordos, Spectroscopic study of atmospheric pressure Argon/Methane capacitively coupled plasma, Studia Chemia, 1 (2011) 7-16.

Title: Spectroscopic study of atmospheric pressure Argon/Methane capacitively coupled plasma

Abstract: The emission spectrum (200 – 1000 nm) and discharge characteristics of an atmospheric pressure Ar/CH4 capacitively coupled plasma, 275 W, 27.12 MHz, 0.7 L min-1 Ar and 0-7.5 mL min-1 CH4 as collision/reaction gas were studied. The emission spectrum of pure Ar plasma is dominated by molecular bands of OH and N2 second positive system in UV as well as Ar I (4p→4s) lines in VIS range. The addition of CH4 results in the appearance of the C2 Swan band and quenching of OH, N2 and Ar emission. Quenching is the consequence of the second-kind collisions of CH4 molecule with Ar, N2 excited species and chemical reaction with OH radical, respectively. Processes were confirmed by the decrease of the excitation temperature of Ar and electron number density when adding CH4 in Ar plasma. The Ar/CH4 plasma is of great interest for applications in atomic spectroscopy due to the possibility to remove spectral interferences by the collision/reaction gas method and the use of low resolution microspectrometers.

Keywords: capacitively coupled plasma, molecular emission, collision/reaction gas, plasma diagnosis