Determination of N and O‐atoms and N₂ (A) Metastable Molecule Densities in the Afterglows of N₂‐H₂, Ar‐N₂‐H₂ and Ar‐N₂‐O₂ Microwave Discharges

Abstract

Key words Optical emission spectroscopy, microwave flowing afterglows, N2-H2, Ar-N2-H2, Ar-N2-O2 gas mixtures, N density, O density, N2 (A) density.Early afterglows of N 2-H2, Ar-N2-H2 and Ar-N2-O2 flowing microwave discharges are characterized by optical emission spectroscopy. The N and O atoms and the N2(A) metastable molecule densities are determined by optical emission spectroscopy after calibration by NO titration for N and O-atoms and measurements of NO and N2 band intensities. If an uncertainty of 30% is estimated on N-atomic density, an inaccuracy of one order of magnitude is obtained on the O and N2 (A) densities. In N2-(0.05-2.5%)H2 and Ar-(1-50%)N2-(0.05-2.5%) H2 gas mixtures, the O-atoms are coming from O2 impurities in the discharge. Concentrations of N and O-atoms and of N2 (A) densities are compared to the ones obtained in Ar-(5-50%)N2-(0.2-2.5%) O2 gas mixtures in which a controlled amount of O2 is added.

Quantitative evaluation of the densities of active species of N2 in the afterglow of Ar-embedded N2 RF plasma

“…Compared to the vibrational sequence of the N 2 emission band around 580 nm in the early afterglow (z ¼ 34 cm), the population of excited N 2 (B, 11) in the late afterglow (z ¼ 56 cm) is significantly enhanced than that of N 2 (B, 9). The origin of such drastic enhancement is largely due to the contribution of following reactions which are the main characteristics of the late afterglow [12,13,26,27].…”

“…As recently studied in N 2 and AreN 2 microwave afterglows [27], the k 3 factor obtained from pure N 2 can be used for the Ar-20%N 2 gas mixtures. Thus, by using the k 3 calibration factor, the relative intensities at 580 nm (I m 580 ) and the a NþN value can be used to determine the N atom density.…”

“…where q ðX; v À C; v 0 Þ is the FranckeCondon factor, y e (C) and y l (C,v 0 ) are the electron excitation and loss frequencies, with [34], and k Q ðC; v 0 Þ ¼ the collisional quenching rate by the N 2 molecules, which can be neglected in front of v R ðC; v 0 Þ for P > 5 Torr [27].…”

“…(580 nm) to obtain the N 2 (A) and N þ 2 densities from that of N-atoms. This line-ratio method has been successfully used for the characterization of microwave [26e28] and RF [12,13] afterglows of N 2 [12,26], N 2 eH 2 [13,27,28] and N 2 eO 2 [26] mixtures.…”

Unexpected Chemical and Thermal Stability of Surface Oxynitride of Anatase TiO2 Nanocrystals Prepared in the Afterglow of N2 Plasma

“…In addition, the active nitrogen species in the N 2 plasmas and their afterglows can be controlled by changing the process parameters such as pressure, flow rate and the applied power [10][11][12][13][14][15][16][17]. Various excited states of neutral N 2 , N 2 + ions and atomic N species are generated in the N 2 plasmas and in their afterglows under moderate operating conditions [10,11,15,16,18] and their widely different lifetimes make the densities of the excited species in the afterglow region change along the downstream of the gas flow.…”