Metastable atoms and the electron distribution function in a helium discharge positive column

Alexandrov, V M; Flender, U; Kolokolov, N. B.; Rykova, O. V.; Wiesemann, K.

doi:10.1088/0963-0252/5/3/021

Cited by 12 publications

(7 citation statements)

References 18 publications

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“…3 which is in agreement with the observed electron energy distribution in helium discharge [20], where the energy continuously decreases into area of the first ionization potentials with an energy maximum of several electron volts. The lines of atomic hydrogen H I (a-Brackett series at 2,467.73 cm -1 * 13.0 eV) for CF 3 CHFCF 3 and atomic bromine Br I (e.g., transitions at 4,372.07 cm -1 ) for CF 3 Br were observed as well.…”

Section: Ftir Emission Spectrasupporting

confidence: 89%

Time-Resolved Fourier Transform Emission Spectroscopy of CF3Br and CF3CFHCF3 in a Pulsed Electrical Discharge

Ferus

Civiš

Kubelík

et al. 2011

Plasma Chem Plasma Process

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The environmentally important decomposition of halogenated species CF 3 Br and CF 3 CHFCF 3 in helium discharge plasma was investigated by time-resolved high-resolution Fourier transform infrared emission spectroscopy. Contrary to classical pyrolysis, a deeper fragmentation of precursors up to atoms and lower molecular species was observed. Excited molecular products CF, CF 2 and CF 4 achieved the maximal concentration in the afterglow. The high concentration of all these species is in agreement with a kinetic model based on radical chemistry. The non-detectable concentration of CF 3 can be connected to its high reactivity and the formation of more stable products, CF 4 and CF 2 , by addition or release of a fluorine atom, respectively. Other products included HF, HBr, CO and cyano compounds that were produced by secondary reactions with traces of water vapor, atmospheric oxygen and nitrogen present in original industrial samples as impurities.

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Section: Ftir Emission Spectrasupporting

confidence: 89%

Time-Resolved Fourier Transform Emission Spectroscopy of CF3Br and CF3CFHCF3 in a Pulsed Electrical Discharge

Ferus

Civiš

Kubelík

et al. 2011

Plasma Chem Plasma Process

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“…Our experimental set-up consisted of the discharge tube described in [21]. It is made from Duran glass and has a diameter of 4 cm and as electrodes aluminium cylinders of 2.4 cm diameter, 6 cm long, situated in side arms, 64 cm apart from each other [21]. A set of three cylindrical platinum probes was mounted 57 cm away from the cathode arm.…”

Section: Methodsmentioning

confidence: 99%

A comparative study of the electron distribution function in the positive columns in and /He dc glow discharges by optical spectroscopy and probes

Bibinov

Kokh

Kolokolov

et al. 1998

Plasma Sources Sci. Technol.

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We compare to the probe method a spectroscopic method for determining in plasmas the electron distribution function (EDF) over a wide energy range. For a test of the radiative-collisional model we use to describe the plasma radiation, the measured vibrational distributions of N 2 (C-B) and N + 2 (B-X) were compared with calculated ones using our model and EDFs measured by Langmuir probes. From this comparison we obtain a value for the rate constant for vibrational relaxation at the walls. In a second step we invert the system of model equations for obtaining the EDF from measured line intensities. From the vibrational structure of the emission spectra of the nitrogen molecule the EDF is obtained in the energy range of 1.5-4.5 eV. From the relative intensities of the emission of nitrogen molecules and helium atoms the EDF for electron energies above 11 eV is derived. In the region between these ranges the EDF is interpolated. The results agree within the limits of the experimental errors with the EDF measured directly by the probe.

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“…Therefore, a collisional-radiative (CR) model taking account of all relevant excitation and de-excitation processes is required [17]. Especially the metastable levels of argon (1s 3 , 1s 5 ) and helium (2 1 S, 2 3 S) having long lifetimes may affect the ionization [18] and the population of higher levels [19,20] due to electron impact excitation from metastable levels. By adjusting the line intensities deduced to the measured values we can determine the plasma parameters.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic investigations of electron heating in a high-density helicon discharge

Clarenbach¹,

Krämer²,

Lorenz³

2007

J. Phys. D: Appl. Phys.

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The evolution of a high-density helicon discharge in argon and argon–helium mixtures was studied by spectroscopic methods as well as standard diagnostics. Applying optical emission spectroscopy, the electron temperature was deduced from the ratio of different emission lines. The spectral data were evaluated using collisional-radiative (CR) models taking account of secondary processes like the transitions between excited levels and excitation from metastable niveaus. In addition, time-resolved laser absorption spectroscopy was applied to determine the temperature and the density of the Ar*(3P0) metastable atoms from the absorption profile of the 772.42 nm argon line. Due to strong coupling by electron collisions, the temperature of the metastable atoms up to 1000 K reflects the gas temperature of the ground state atoms. The gas temperature and the gas density, which is readily obtained from the temperature, are needed as input parameters for the CR models. The spectroscopic results were compared with Langmuir probe measurements which partially utilized passive compensation. The main issue of this study is electron heating due to helicon wave absorption. Applying a double radio-frequency (rf) pulse technique with variable rf power in the second pulse, the growth of the electron temperature was measured as a function of rf power. To clarify whether or not fast electrons are generated in the helicon wave due to resonant electron heating, phase-sensitive emission measurements of the Ar II (480 nm) line with a short lifetime (τ ≈ 7 ns) were performed on the rf time-scale (period 73.7 ns). However, no modulation of the Ar II emission synchronous with the helicon phase was observed. Rather, the temporal growth of the electron temperature reveals the electrons to be predominantly heated in the bulk of the energy distribution function.

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Metastable atoms and the electron distribution function in a helium discharge positive column

Cited by 12 publications

References 18 publications

Time-Resolved Fourier Transform Emission Spectroscopy of CF3Br and CF3CFHCF3 in a Pulsed Electrical Discharge

Time-Resolved Fourier Transform Emission Spectroscopy of CF3Br and CF3CFHCF3 in a Pulsed Electrical Discharge

A comparative study of the electron distribution function in the positive columns in and /He dc glow discharges by optical spectroscopy and probes

Spectroscopic investigations of electron heating in a high-density helicon discharge

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