Hydrogen Balmer alpha line shapes for hydrogen-argon mixtures in a low-pressure rf discharge

Djurović, S.; Roberts, James R.

doi:10.1063/1.355117

Cited by 61 publications

(57 citation statements)

References 30 publications

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“…<1 Torr) pure hydrogen, and RF and DC generated H 2 /Ar plasmas [1][2][3][4][5][6][7][8][9][10]. New reports continue to appear [11], and now there are several reports from our team that selective H α line broadening is found in other plasmas called resonant-transfer (rt)-plasmas including H 2 /He (RF-GEC-type cell, [12]), water (microwave [13] and RF-GEC-type cell [14]) and in the presence of certain catalysts including helium, argon, potassium, and strontium (glow discharge, RF-GEC, and filament-type cells [15][16][17][18][19][20][21][22]).…”

Section: Introductionmentioning

confidence: 99%

Evidence of catalytic production of hot hydrogen in RF generated hydrogen/argon plasmas

Phillips

Chen

Akhtar

et al. 2007

International Journal of Hydrogen Energy

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This is the third in a series of papers by our team on apparently anomalous Balmer series line broadening in hydrogen containing RF generated, low pressure (< 600 mTorr) plasmas. In this paper the selective broadening of the atomic hydrogen lines in pure H 2 and Ar/H 2 mixtures in a large 'GEC' cell (36 cm length × 14 cm ID) was mapped as a function of position, H 2 /Ar ratio, time, power, and pressure. Several observations regarding the selective line broadening were particularly notable as they are unanticipated on the basis of earlier models. First, the anomalous broadening of the Balmer lines was found to exist throughout the plasma, and not just in the region between the electrodes. Second, the broadening was consistently a complex function of the operating parameters particularly gas composition (highest in pure H 2 ), position, power, time and pressure. Clearly not anticipated by earlier models were the findings that under some conditions the highest concentration of 'hot' (>10 eV) hydrogen was found at the entry end, and not in the high field region between the electrodes and that in other conditions, the hottest H was at the (exit) pump (also grounded electrode) end. Third, excitation and electron temperatures were less than one eV in all regions of the plasma not directly adjacent (>1mm) to the electrodes, a Corresponding author: phone 505-665-2682; fax 505-665-5548 jphillips@LanL.gov 2 providing additional evidence that the energy for broadening, contrary to standard models, is not obtained from the field. Fourth, in contrast to our earlier studies of hydrogen/helium and water plasmas, we found that in some conditions 98% of the atomic hydrogen was in the 'hot' state throughout the GEC-type cell. Virtually every operating parameter studied impacted the character of the hot H atom population, and clearly second and third order effects exist, indicating a need for experimental design. Some non-field mechanisms for generating hot hydrogen atoms, specifically those suggested by Mills' CQM model, are outlined.3

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Section: Introductionmentioning

confidence: 99%

Evidence of catalytic production of hot hydrogen in RF generated hydrogen/argon plasmas

Phillips

Chen

Akhtar

et al. 2007

International Journal of Hydrogen Energy

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“…Many groups report (anomalous) line broadening of atomic hydrogen lines in mixed gas plasmas containing argon in high field regions [6][7][8][9][10][11][12][13][14][15][16][17]. A similar phenomenon has been observed in pure hydrogen plasmas, generated with DC discharge or RF systems including one group using a GEC cell [4,7,17].…”

Section: Discussionmentioning

confidence: 87%

“…Recently, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] unique and dramatic H α line broadening has been observed in a variety of laboratories in specific mixed gas plasmas, particularly Ar/H 2 plasmas, operated at low pressure (milli-Torr) and generated, with microwave and glow discharge systems. It is universally agreed that the broadening must be Doppler broadening.…”

Section: Introductionmentioning

confidence: 99%

“…One class of mechanisms can be called field acceleration (FA) models because, in all the various permutations of this class of models, it is necessary for the energy to be given to the hydrogen from the field. For example, it is postulated that ionic molecular hydrogen is accelerated in the cathode fall region, then is neutralized and picks up charge from Ar ions, and finally dissociates and emits [6][7][8][9][10][11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

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Evidence of catalytic production of hot atomic hydrogen in RF generated hydrogen/helium plasmas

Phillips¹,

Chen²

2008

International Journal of Hydrogen Energy

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A study of the line shapes of hydrogen Balmer series lines in RF generated low pressure H 2 /He plasmas produced results suggesting a catalytic process between helium and hydrogen species results in the generation of 'hot' (ca. 28 eV) atomic hydrogen.Even far from the electrodes 'hot' atomic hydrogen was predominant in H 2 /He plasmas.Line shapes, relative line areas of cold and hot atomic hydrogen (hot/cold>2.5), were very similar for areas between the electrodes and far from the electrodes for these plasmas. In contrast, in H 2 /Xe only 'warm' (<5 eV) hydrogen (warm/cold<1.0) was found between the electrodes, and only cold hydrogen away from the electrodes. Earlier postulates that preferential hydrogen line broadening in plasmas results from the acceleration of ionic hydrogen in the vicinity of electrodes, and the special charge exchange characteristics of Ar/H 2 + are clearly belied by the present results that show atomic hydrogen line shape are similar for H 2 /He plasmas throughout the relatively large cylindrical (14 cm ID x 36 cm length) cavity.

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“…Anomalous, even extreme, hydrogen line broadening was found in a number of mixed discharge plasmas excited via direct current ͑dc͒ or radio frequency ͑rf͒ electric fields. [1][2][3][4][5] The Balmer line spectra emitted by these discharges have typical multimode behavior, with widely broadened "wings" ͑"fast" hydrogen͒ and a sharp top ͑"slow" hydrogen͒. The results have usually been explained in terms of Doppler shift and broadening due to the acceleration of charges ͑such as H + , H 2 + , and H 3 + ions͒ in the high dc electric fields present in the sheath regions of these discharges.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic investigation of wave driven microwave plasmas

Wijtvliet

Felizardo²,

Tatarova³

et al. 2009

Journal of Applied Physics

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Large H atom line broadening was found throughout the volume of surface wave generated He-H 2 and H 2 microwave plasmas at low pressures. The measured Doppler temperatures corresponding to the H ␤ , H ␥ , H ␦ , H , and H line profiles were found to be higher than the rotational temperature of the hydrogen molecular Fulcher-␣ band and the Doppler temperature of the 667.1 nm singlet He line. No excessive broadening has been found. The Lorentzian and Gaussian widths as determined by fitting the spectral lines with a Voigt profile increase with the principal quantum number of the upper level. In contrast, no such dependence for the Gaussian width has been observed in an Ar-H 2 discharge. No population inversion has been observed from measurements of the relative intensities of transitions within the Balmer series.

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Hydrogen Balmer alpha line shapes for hydrogen-argon mixtures in a low-pressure rf discharge

Cited by 61 publications

References 30 publications

Evidence of catalytic production of hot hydrogen in RF generated hydrogen/argon plasmas

Evidence of catalytic production of hot hydrogen in RF generated hydrogen/argon plasmas

Evidence of catalytic production of hot atomic hydrogen in RF generated hydrogen/helium plasmas

Spectroscopic investigation of wave driven microwave plasmas

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