Optical emission spectroscopy of CO₂ glow discharge at low pressure

Abstract

Abstract Optical emission spectroscopy was used to study the glow discharge of CO 2 in the pressure range of 0.2 to 1.2 mTorr, power of 160 W and a flux of 35 psi. The emission bands and lines were measured using a monochromator in the wavelength range of 200 to 900 nm. The species observed were C 2 (A 3 Π g – X '3 Π u ) at 435.7nm and (C' 1 Π g – b 1 Π u ) at 369.2 nm; O 2 (b 1 Σ g + ‐ X 3 Σ g – ) at 628.2; CO (a' 3 Σ ‐ a 3 Π) at 674.7 nm; O 2 + (A 2 Π u ‐ X 2 Π g ) at 339.3 and 289.2 nm; CO 2 + (A 2 Π ‐ X 2 Π) at 353.2 nm; CO 2 ( 1 B 2 – X 1 Σ + ) at 391.7 nm; CO + (A 2 Π – X 2 Σ) at 577.7 nm; and O 3 ( 1 B 2 – X 1 A 1 ) at 327.2 nm. We observed that the emission intensities bands have an almost constant behavior as function of the pressure in the range of 0.2 to 0.6 mTorr, followed by an increasing behavior. The electron temperature and ion density were determined by a double Langmuir probe. The electron temperature was found of 8.53 eV, and the electron concentration of 7.11 x 10 9 cm –3 at a pressure of 0.8 mTorr. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)