Measurements and analysis of rotational temperatures obtained with Raman and optical emission spectroscopy in a nonequilibrium nitrogen plasma
Abstract Rotational temperature measurements of N 2 (B 3 Π g ), N 2 (C 3 Π u ) and N 2 + ( B 2 Σ u + ) obtained by optical emission spectroscopy (OES) are compared with previous gas temperature measurements obtained with Raman spectroscopy in a nonequilibrium recombining nitrogen plasma at atmospher...
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Published in | Plasma sources science & technology Vol. 30; no. 12; pp. 125019 - 125031 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
IOP Publishing
01.12.2021
|
Subjects | |
Online Access | Get full text |
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Summary: | Abstract
Rotational temperature measurements of N
2
(B
3
Π
g
), N
2
(C
3
Π
u
) and
N
2
+
(
B
2
Σ
u
+
)
obtained by optical emission spectroscopy (OES) are compared with previous gas temperature measurements obtained with Raman spectroscopy in a nonequilibrium recombining nitrogen plasma at atmospheric pressure. The plasma is produced in a state of thermal and chemical equilibrium at about 7000 K using an inductively coupled plasma torch. It is then forced out of chemical equilibrium by imposing rapid cooling through a water-cooled tube. The gas temperature measured by Raman spectroscopy is about 3200 K at the exit of the tube. The rotational temperatures of N
2
(B) and N
2
(C) measured with OES are found to be in good agreement with the gas temperature, but the rotational temperature of N
2
+
(B) is found to be significantly above the gas translational temperature. We propose that this higher rotational temperature is the result of N
2
+
(B) being formed by the charge exchange reaction between N
2
(A
3
Σ
u
+
) and N
+
. Kinetic and QSS simulations are performed to support this assumption and a rate constant for this reaction is proposed. |
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Bibliography: | PSST-104260.R2 |
ISSN: | 0963-0252 1361-6595 |
DOI: | 10.1088/1361-6595/ac2223 |