An experimental comparison of rotational temperature and gas kinetic temperature in a discharge

Goyette, A. N.; Jameson, W B; Anderson, L. W.; Lawler, J. E.

doi:10.1088/0022-3727/29/5/013

Cited by 35 publications

(19 citation statements)

References 12 publications

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“…Additional references are, e.g., [192,193]. While many researchers report that the Fulcher α band is reliable, there exist plasma conditions for which the Fulcher α band rotational temperature does not correlate to the gas temperature [194].…”

Section: Short Overview Of Often-used Ro-vibrational Transitionsmentioning

confidence: 99%

Gas temperature determination from rotational lines in non-equilibrium plasmas: a review

Bruggeman

Sadeghi

Schram

et al. 2014

Plasma Sources Sci. Technol.

435

431

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The gas temperature in non-equilibrium plasmas is often obtained from the plasma-induced emission by measuring the rotational temperature of a diatomic molecule in its excited state. This is motivated by both tradition and the availability of low budget spectrometers. However, non-thermal plasmas do not automatically guarantee that the rotational distribution in the monitored vibrational level of the diatomic molecule is in equilibrium with the translational (gas) temperature. Often non-Boltzmann rotational molecular spectra are found in non-equilibrium plasmas. The deduction of a gas temperature from these non-thermal distributions must be done with care as clearly the equilibrium between translational and rotational degrees of freedom cannot be achieved. In this contribution different methods and approaches to determine the gas temperature are evaluated and discussed. A detailed analysis of the gas temperature determination from rotational spectra is performed. The physical and chemical background of non-equilibrium rotational population distributions in molecular spectra is discussed and a large range of conditions for which non-equilibrium occurs are identified. Fitting procedures which are used to fit (non-equilibrium) rotational distributions are analyzed in detail. Lastly, recommendations concerning the conditions for which the gas temperatures can be obtained from diatomic spectra are formulated.

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Section: Short Overview Of Often-used Ro-vibrational Transitionsmentioning

confidence: 99%

Gas temperature determination from rotational lines in non-equilibrium plasmas: a review

Bruggeman

Sadeghi

Schram

et al. 2014

Plasma Sources Sci. Technol.

435

431

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“…2,3 Yet, despite the dominance of H 2 in the process gas, relatively few OES studies of the diamond CVD environment have focussed on the information that could be provided by analysis of the H 2 emissions. [4][5][6][7][8] H 2 shows a wealth of rovibrational structure in the visible and near infrared (IR) spectral regions associated with transitions between bound excited electronic states. [9][10][11] Most prior experimental studies of MW activated hydrogen-containing plasmas have focussed on the d 3 Π u −a 3 Σ g + (Fulcher) system, 5 and a 3 Σ g + −b 3 Σ u + continuum emission 27,28 have been used for plasma diagnostics and limited studies have been undertaken using the e 3 Σ u + −a 3 Σ g + system.…”

Section: Introductionmentioning

confidence: 99%

Spatially Resolved Optical Emission and Modeling Studies of Microwave-Activated Hydrogen Plasmas Operating under Conditions Relevant for Diamond Chemical Vapor Deposition

et al. 2018

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A microwave (MW) activated hydrogen plasma operating under conditions relevant to contemporary diamond chemical vapor deposition reactors has been investigated using a combination of experiment and self-consistent 2-D modeling. The experimental study returns spatially and wavelength resolved optical emission spectra of the d → a (Fulcher), G → B, and e → a emissions of molecular hydrogen and of the Balmer-α emission of atomic hydrogen as functions of pressure, applied MW power, and substrate diameter. The modeling contains specific blocks devoted to calculating (i) the MW electromagnetic fields (using Maxwell's equations) self-consistently with (ii) the plasma chemistry and electron kinetics, (iii) heat and species transfer, and (iv) gas−surface interactions. Comparing the experimental and model outputs allows characterization of the dominant plasma (and plasma emission) generation mechanisms, identifies important coupling reactions between hydrogen atoms and molecules (e.g., the quenching of H(n > 2) atoms and electronically excited H 2 molecules (H 2 *) by the alternate ground-state species and H 3 + ion formation by the associative ionization reaction of H(n = 2) atoms with H 2 ), and illustrates how spatially resolved H 2 * (and H α ) emission measurements offer a detailed and sensitive probe of the hyperthermal component of the electron energy distribution function.

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“…The T g of heavy species can be deduced from the rotational temperature (T r ) due to the strong coupling between translational and rotational energy states [30]. At atmospheric pressure, the OH radical's T r could be accepted as an estimate of the T g [31]. Figure 18 presents that the T r of OH radicals increased from 400 K to 600 K with the applied voltage from −22 kV to −26 kV at the pulsed frequency of 50 Hz.…”

Section: T G Measurementmentioning

confidence: 99%

Spectroscopic diagnosis of plasma in atmospheric pressure negative pulsed gas-liquid discharge with nozzle-cylinder electrode

Sun¹,

TAO²,

ZHU³

et al. 2018

Plasma Sci. Technol.

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The plasma characteristics of a gas-liquid phase discharge reactor were investigated by optical and electrical methods. The nozzle-cylinder electrode in the discharge reactor was supplied with a negative nanosecond pulsed generator. The optical emission spectrum diagnosis revealed that OH (A 2 ∑ + →X 2 Π, 306-309 nm), N 2 (C 3 Π→B 3 Π g , 337 nm), O (3p 5 p→3s 5 s 0 , 777.2 nm) and O (3p 3 p→3s 3 s 0 , 844.6 nm) were produced in the discharge plasma channels. The electron temperature (T e) was calculated from the emission relative intensity ratio between the atomic O 777.2 nm and 844.6 nm, and it increased with the applied voltage and the pulsed frequency and fell within the range of 0.5-0.8 eV. The gas temperature (T g) that was measured by Lifbase was in a range from 400 K to 600 K.

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An experimental comparison of rotational temperature and gas kinetic temperature in a discharge

Cited by 35 publications

References 12 publications

Gas temperature determination from rotational lines in non-equilibrium plasmas: a review

Gas temperature determination from rotational lines in non-equilibrium plasmas: a review

Spatially Resolved Optical Emission and Modeling Studies of Microwave-Activated Hydrogen Plasmas Operating under Conditions Relevant for Diamond Chemical Vapor Deposition

Spectroscopic diagnosis of plasma in atmospheric pressure negative pulsed gas-liquid discharge with nozzle-cylinder electrode

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