Mechanism of N2 dissociation and kinetics of N(4S) atoms in pure nitrogen plasma

6th International Workshop & Summer School on Plasma Physics 2014

Volynets, A.V.^1,2 ; Lopaev, D.V.^2 ; Popov, N.A.^2

Lomonosov Moscow State University, Faculty of Physics, Leninskie Gory, Moscow

119991, Russia^1

Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, Leninskie gory, GSP-1, Moscow

119991, Russia^2

关键词: DC glow discharge;    Discharge conditions;    Discharge parameters;    Dissociation mechanisms;    Dissociation rates;    Phenomenological modeling;    Surface loss probabilities;    Vibrational excitation;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/768/1/012006/pdf
DOI  :  10.1088/1742-6596/768/1/012006

来源: IOP

【 摘 要 】

This work deals with kinetics of the ground state nitrogen atoms N(4S) and N2dissociation mechanism in pure nitrogen plasma. The experiment was carried out in positive column of DC glow discharge at a range of parameters p = 5 - 50 Torr, J = 20 - 100 mA. The use of axial homogeneous glow discharge allowed considering N(4S) balance for spatially uniform conditions controlled by only two terms: source (characterized by effective production rate kdisseff) and loss (characterized by effective loss time τNloss). Analysis of these parameters gains considerably better understanding of N2 dissociation mechanism in pure nitrogen plasma that was the main goal of the given work. So N/N2dissociation rate as function of discharge parameters was obtained using two independent emission optical methods: actinometry on Ar atoms and N22+ band emission decay at discharge modulation. Measurements of N/N2radial profiles allowed estimating N atom surface loss probability γNlossand correspondingly τNloss. It was revealed that γNlossdepends on N(4S) concentration and thereby discharge conditions through the sorption balance of physisorbed N atoms. Simple phenomenological model taking into account basic surface processes provides γNlossdata in good agreement with experiment. Finally, kdisseffwas obtained as function of reduced electric field E/N and it was shown that even EEDF self-consistently calculated with accounting for N2vibrational excitation is unable to provide observed values of kdisseff. Reasons of that fact are discussed in detail.