Absolute H-atom concentration profiles in continuous and pulsed rf discharges

Tserepi, Angeliki; Dunlop, James R.; Preppernau, Bryan L.; Miller, Terry A.

doi:10.1063/1.351564

Cited by 40 publications

(24 citation statements)

References 13 publications

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“…The secondary reactions OHϩOH→H 2 OϩO and OϩOH→O 2 ϩH are significantly reduced at the low H concentrations in the flow-tube reactor, 17,48 and other interfering reactions such as OϩNO 2 →O 2 ϩNO and OHϩH 2 →H 2 OϩH are made negligible by diluting both NO 2 and H 2 in He. 17 The second equality in Eq. ͑7͒ implies the assumption of efficient mixing between the NO 2 /He flow from the titration tube and the main flow.…”

Section: A Titration In a Flow-tube Reactormentioning

confidence: 99%

“…In this approach often a ''flow-tube reactor'' is used as a source of ground-state atomic radicals, in which the concentration of these radicals is determined by a chemical titration. This method is based on well-established flow reactor and titration techniques in chemistry 24 and has been applied for the calibration of LIF density measurements of several atomic radicals in plasmas, including atomic hydrogen 17,25 and atomic oxygen. 26 Another approach is to also use an independent quantitative measurement technique to determine the density of the probed species.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative two-photon laser-induced fluorescence measurements of atomic hydrogen densities, temperatures, and velocities in an expanding thermal plasma

Boogaarts

Mazouffre

Brinkman

et al. 2002

Review of Scientific Instruments

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We report on quantitative, spatially resolved density, temperature, and velocity measurements on ground-state atomic hydrogen in an expanding thermal Ar-H plasma using two-photon excitation laser-induced fluorescence ͑LIF͒. The method's diagnostic value for application in this plasma is assessed by identifying and evaluating the possibly disturbing factors on the interpretation of the LIF signal in terms of density, temperature, and velocity. In order to obtain quantitative density numbers, the LIF setup is calibrated for H measurements using two different methods. A commonly applied calibration method, in which the LIF signal from a, by titration, known amount of H generated by a flow-tube reactor is used as a reference, is compared to a rather new calibration method, in which the H density in the plasma jet is derived from a measurement of the two-photon LIF signal generated from krypton at a well-known pressure, using a known Kr to H detection sensitivity ratio. The two methods yield nearly the same result, which validates the new H density calibration. Gauging the new ''rare gas method'' by the ''flow-tube reactor method,'' we find a krypton to hydrogen two-photon excitation cross section ratio Kr ͑2͒ / H (2) of 0.56, close to the reported value of 0.62. Since the H density calibration via two-photon LIF of krypton is experimentally far more easy than the one using a flow-tube reactor, it is foreseen that the ''rare gas method'' will become the method of choice in two-photon LIF experiments. The current two-photon LIF detection limit for H in the Ar-H plasma jet is 10 15 m Ϫ3 . The accuracy of the density measurements depends on the accuracy of the calibration, which is currently limited to 33%. The reproducibility depends on the signal-to-noise ͑S/N͒ ratio in the LIF measurements and is orders of magnitude better. The accuracy in the temperature determination also depends on the S/N ratio of the LIF signal and on the ratio between the Doppler-width of the transition and the linewidth of the excitation laser. Due to the small H mass, the current linewidth of the UV laser radiation is never the accuracy limiting factor in the H temperature determination, even not at room temperature. Quantitative velocity numbers are obtained by measuring the Doppler shift in the H two-photon excitation spectrum. Both the radial and axial velocity components are obtained by applying a perpendicular and an antiparallel excitation configuration, respectively. The required laser frequency calibration is accomplished by simultaneously recording the I 2 absorption spectrum with the fundamental frequency component of the laser system. This method, which is well-established in spectroscopic applications, enables us to achieve a relative accuracy in the transition frequency measurement below 10 Ϫ6 , corresponding to an accuracy in the velocity of approximately 200 m/s. This accuracy is nearly laser linewidth limited.

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Section: A Titration In a Flow-tube Reactormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative two-photon laser-induced fluorescence measurements of atomic hydrogen densities, temperatures, and velocities in an expanding thermal plasma

Boogaarts

Mazouffre

Brinkman

et al. 2002

Review of Scientific Instruments

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“…6 More recently, advanced non-linear optical crystals, such as the BBO, have replaced the less efficient long path Raman cells to generate the required ultraviolet laser light, down to nearly 200 nm, for atomic TALIF methods. 7 The TALIF technique has been demonstrated for several small atoms, 6,8,9 but can present a challenge in achieving good detection sensitivity since, in general, a two-photon excitation cross section will be vastly smaller than that of a typical one photon process.…”

Section: Introductionmentioning

confidence: 99%

Two-photon absorption laser-induced fluorescence of atomic nitrogen by an alternative excitation scheme

Adams

Miller

1998

Chemical Physics Letters

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“…At 1.35 mbar, an upper bound on the O concentration in the plasma is 2;10 cm\ from NO titration [23]. Since the signal to noise ratio is about 220 using 300 J, our detection limit Fig.…”

Section: Oxygen Atom Studymentioning

confidence: 87%

“…45 #NO [23]. The length of the active zone is about 3.5 cm downstream from the microwave cavity at 1.3 mbar total pressure.…”

Section: Microwave Dischargementioning

confidence: 99%

Atomic oxygen detection using two-photon degenerate four wave mixing

Picard

Grisch

Attal‐Trétout

et al. 1997

Z Phys D - Atoms, Molecules and Clusters

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We report a new application of Forward Degenerate Four Wave Mixing to the two-photon transition 2pP3p of atomic oxygen. This spectroscopy has been used to detect oxygen atoms produced in a microwave discharge. The possibility to determine number densities over a range of microwave plasma parameters is investigated. In contrast to conventional linear techniques, quantitative data are relatively easy to obtain even for environments with high background luminosity, limited optical access and inhomogeneous quenching.

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Absolute H-atom concentration profiles in continuous and pulsed rf discharges

Cited by 40 publications

References 13 publications

Quantitative two-photon laser-induced fluorescence measurements of atomic hydrogen densities, temperatures, and velocities in an expanding thermal plasma

Quantitative two-photon laser-induced fluorescence measurements of atomic hydrogen densities, temperatures, and velocities in an expanding thermal plasma

Two-photon absorption laser-induced fluorescence of atomic nitrogen by an alternative excitation scheme

Atomic oxygen detection using two-photon degenerate four wave mixing

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