Excitation equilibria in plasmas; a classification

A supersonically expanding argon cascaded arc plasma, with difFerent amounts of hydrogen added (0, 0.7, and 1. 4 vol % H2), was studied using Thomson-Rayleigh scattering and optical emission spectroscopy. %'ith hydrogen added, the electron density profile as a function of the distance from the onset of the expansion shows a large extra ionization loss {compared to the pure argon case), especially after the stationary shock front. This anomalous loss of ionization is attributed to molecular processes, such as associative charge transfer between Ar+ and H2, and dissociative recombination of the resulting ArH+ molecular ion. Spatially resolved emission spectroscopy shows that in the expansion the radial hydrogen emission profiles are broader than the argon profiles. The addition of hydrogen appears to change the characteristic shock behavior of pure argon. For both the argon and the hydrogen system it is shown that the uppermost levels are in Saha equilibrium with their adjacent continuum.

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“…(6) and (7) as the first step (6) (12) In (12), t =0 corresponds to z = 70 mm, whereas t = t corresponds to z =500 mm (see Fig. 4).…”

Section: A Thomson-rayleigh Scattering Resultsmentioning

confidence: 99%

Argon-hydrogen plasma jet investigated by active and passive spectroscopic means

et al. 1994

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“…The often used assumption of partial Local Thermodynamic Equilibrium (pLTE) means that top atomic levels obey the Saha equation and Boltzmann statistics. In that case the excitation temperature (T exc ) derived from the Boltzmann plot [19] should be equivalent to the electron temperature [20][21][22]. Some authors [23] have used a direct but experimentally challenging technique of Thomson scattering to determine the electron temperature.…”

Section: Excitation Temperature Estimated From Ar I Linesmentioning

confidence: 99%

Time resolved optical emission spectroscopy in power modulated atmospheric pressure plasma jet

2014

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Abstract:In this paper, the effects of the power modulation on atmospheric pressure plasma jet, operated in Ar+2%N 2 mixture, are studied. Time resolved optical emission spectroscopy is used for the investigation. From line and band intensities, the excitation, vibration and rotation temperatures are calculated. Their evolution during the modulation period exhibits a strong dependence on modulation frequency. For higher modulation frequencies, there is significant discrepancy in rotational temperatures calculated from OH spectra and from N 2 + spectra, which indicates that thermalisation time can reach milliseconds.

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“…In addition, T exc generally lies between the gas temperature and the electron temperature and shows the same tendency as the electron temperature. 12,13 On the other hand, the gas temperature ͑T gas ͒ was determined by measuring the rotational temperature ͑T rot ͒, which was measured by analyzing the diatomic molecular spectra, since the frequent collisions between heavy particles can equilibrate T gas and T rot in atmospheric pressure plasmas. 14 As the plasma was produced in ambient air, OH molecular lines ͑A 2 ⌺ + , =0→ X 2 ⌸, Ј= 0, 306-310 nm͒ were observed in the emission spectrum due to the water molecules in the air and impurities in the Ar feed gas.…”

Section: A Spatial Measurements Of Plasma Parametersmentioning

confidence: 99%

Parametric study of atmospheric pressure microwave-induced Ar∕O2 plasmas and the ambient air effect on the plasma

Moon

Choe

2006

Physics of Plasmas

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A torch type microwave-induced afterglow plasma was produced at atmospheric pressure using an open-ended fused silica concentric double tube assisted by Ar and O 2 supply gases. The plasma emerged from the end of the discharge tube and was exposed to ambient air. A parametric study of the plasma characteristics was performed by measuring the temperature, density, and plasma volume as the operational parameters such as microwave power, gas flow rate, and its composition were varied. The excitation temperature ͑T exc ͒ obtained from the Ar I emission spectrum ranged from 3010 to 4350 K and the rotational temperature ͑T rot ͒ measured from the OH and O 2 diatomic molecular spectra ranged from 2250 to 3550 K. The electron density ͑n e ͒ from the H ␤ Stark broadening width at the plasma core was in the range of 6.6 to 7.6ϫ 10 14 cm −3 . The two-dimensional distribution of T exc and T rot was also obtained. Experiments while varying the Ar and O 2 gas flow rate and the O 2 / Ar ratio showed that n e was reduced but T exc was increased as the O 2 flow rate was increased. Using an additional dielectric tube for shielding the plasma from the ambient air demonstrated a significantly enlarged plasma length and lower T rot due to the nitrogen entrainment, as compared to the unshielded case.

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Excitation equilibria in plasmas; a classification

Cited by 312 publications

References 65 publications

Argon-hydrogen plasma jet investigated by active and passive spectroscopic means

Argon-hydrogen plasma jet investigated by active and passive spectroscopic means

Time resolved optical emission spectroscopy in power modulated atmospheric pressure plasma jet

Parametric study of atmospheric pressure microwave-induced Ar∕O2 plasmas and the ambient air effect on the plasma

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