Discussion on population kinetics and number densities of excited species of low‐pressure discharge nitrogen plasma

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The differences in the rotational temperatures between neutral molecules and molecular ions are examined for low-pressure microwave discharge nitrogen plasma and oxygen plasma. For N2 plasma, the rotational temperatures of the second positive system (2PS) and first negative system (1NS) are measured, whereas for O2 plasma, those of the atmospheric absorption band (A-band) and 1NS are measured for neutrals and ions, respectively. The experimentally measured spectra are compared with the theoretically calculated ones to determine the vibrational and rotational temperatures as best fitting parameters. It is found that the ions have a higher rotational temperature than neutrals for the N2 plasma, while both have almost the same temperature for the O2 plasma, for which a discussion is made on the basis of atomic and molecular processes. The difference in the rotational temperature between the neutrals and the ions is also discussed from the viewpoint of the atomic and molecular processes in the plasmas.

Section: Theoretical Backgroundsmentioning

confidence: 99%

Experimental study on difference in molecular rotation temperatures between neutral molecules and molecular ions in nitrogen plasma and oxygen plasma by optical emission spectroscopy measurement

Akatsuka

Kawano

Naoi

et al. 2017

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“…It has already been found that the vibrational population is strongly coupled with electron kinetics. 23) Consequently, we consider that a high T e generally raises T v for general low-pressure nitrogen discharge. However, an obvious decrease in the T v of 2PS was observed for a high admixture ratio of 80-96% of Kr or Xe, as shown in Fig.…”

Section: Vibrational and Rotational Temperaturesmentioning

confidence: 99%

Dissociation degree of nitrogen molecule in low-pressure microwave-discharge nitrogen plasma with various rare-gas admixtures

Kuwano

Nezu

Matsuura

et al. 2016

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The dissociation degree of nitrogen molecules is examined in a microwave discharge nitrogen–rare gas mixture plasma with a total discharge pressure of 1 Torr, by actinometry measurement. Although the spectral line from the excited nitrogen atoms is overlapped by the band spectrum of the N2 first positive system (1PS), the subtraction of the 1PS spectrum fitted theoretically can successfully extract the atomic nitrogen line, which enables actinometry measurement. The nitrogen dissociation degree decreases with increasing mixture ratio of Ar to Kr, whereas it increases with He, which is attributed to the variations in the electron temperature and density. When we dilute the nitrogen with neon, however, we find an anomalous increase in the nitrogen dissociation degree by several orders of magnitude even at a downstream region in the discharge tube. The reason for the dissociation enhancement upon adding neon is discussed in terms of atomic and molecular processes in the plasma.

“…Figure 9(b) indicates that the vibrational temperature T v and the rotational temperature T r of the N 2 C state substantially equal values, T v ; T r ; 0.2 eV. On the other hand, the electron temperature of the microwave discharge plasma 25,26) is as high as 3.2-3.6 eV, which is used to excite the N 2 molecule to the C state in microwave discharge, where the reaction can be formulated as below: 29) S +…”

Section: Comparison Of Vibrational and Rotational Temperatures Of N 2...mentioning

confidence: 99%

“…´-5.0 10 6 sec (for reference, the average lifetime of the C state is 3.65 × 10 −8 sec). 27,29,35) From this estimation, it can be remarked that the influence of the collision with the ground state can be ignored on the distribution of the vibrational distribution of the B state. That is, the vibration distribution of the B state must be conserved till the 1PS-radiation loss to the A state.…”

Section: Comparison Of Vibrational and Rotational Temperatures Of N 2...mentioning

confidence: 99%

See 1 more Smart Citation

Non-equilibrium characteristics of vibrational and rotational temperatures of N₂-B and C States puffed onto argon arc jet plume

Fukukawa

Nezu

Akatsuka

2019

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Band spectra of the first positive (1PS) and the second positive (2PS) systems of nitrogen molecule are analyzed with an optical emission spectroscopy (OES) measurement when N 2 gas is puffed onto the Ar plasma jet. It is found that T v ; T r ; 0.17 eV for the C state, while T v ; 0.28-0.35 eV, and T r ; 0. 038-0.050 eV for the B state, all of which are determined by fitting the theoretically calculated spectrum with those measured experimentally. Since the electron temperature in the observed area is about 0.4 eV, it is naturally considered that the N 2 C states are mainly produced by the resonant energy transfer from the Ar metastable to the N 2 ground state. It is also considered that similar values of T v and T r of the C state are the approximate value of the Ar gas temperature. Meanwhile, the vibrational distribution of the B state shows that the B state is populated not only by the radiative decay of the C state but also from other collisional processes, since the Franck-Condon principle cannot predict the vibrational population of the B state from the C state.