Two-photon laser induced fluorescence and amplified spontaneous emission atom concentration measurements in O2 and H2 discharges

Amorim, J.; Baravian, G.; Touzeau, M.; Jolly, J.

doi:10.1063/1.357723

Cited by 71 publications

(67 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The excitation is monitored by detection of the nonresonant fluorescence on the Balmer-␣ transition at 656.3 nm from the 3d and 3s states to the 2p 2 P j states. Usually it is mentioned that the 3d←1s transition dominates over the 3s←1s transition due to a 7.56 times higher two-photon absorption cross section, 5,19,20 but actually it depends on the degree of saturation of the transition whether the relative population of 3d and 3s is determined by the relative transition strength or rather by the ratio of the statistical weights of the respective quantum states. Moreover, we found evidence for a pure statistical distribution of the population over all the nϭ3 sublevels from an accurate measurement of the lifetime of the excited state, 34 even though the applied laser intensity assures that the transition is far from saturation ͑see Fig.…”

Section: Excitation and Detection Of Ground-state Atomic Hydrogenmentioning

confidence: 99%

“…ASE of Balmer-␣ radiation ͑H ␣ , 656 nm͒ in a two-photon LIF experiment for detection of ground-state H has been reported both for measurements in a flame, 40 as well as for measurements in a glow discharge plasma. 20 In these studies the possibility of explicitly using the ASE signal for the detection of H is investigated. In the experiments on the ETP reported here, no ASE of H ␣ light has been observed.…”

Section: Density Measurementsmentioning

confidence: 99%

“…Since this approach requires the availability of two independent accurate measurement techniques, it is less commonly reported. 20 A third and rather new approach is to generate a LIF signal from a known amount of a different, stable species by an excitation scheme that is very close to the one applied for the atomic radical. The atomic radical density in the plasma can then be determined from the ratio of the LIF signals when the relative detection sensitivity for the two species is known.…”

Section: Introductionmentioning

confidence: 99%

“…In the field of low-temperature plasma research, where the technique is also referred to as ''two-photon absorption laser induced fluorescence ͑TALIF͒, '' there has been a considerable effort on atomic hydrogen detection, with important contributions from the group of Miller 14 -18 and many others. [19][20][21][22][23] In these studies, the H LIF signal from the plasma is used to determine the hydrogen concentration, assuming that the LIF signal intensity is proportional to the ground-state density. The valuable density information gained in these experiments, however, is usually only qualitative in nature, due to one of the few disadvantages of the LIF technique.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

View full text Add to dashboard Cite

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.

show abstract

Section: Excitation and Detection Of Ground-state Atomic Hydrogenmentioning

confidence: 99%

Section: Density Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

View full text Add to dashboard Cite

show abstract

“…Therefore, the measurement of these atoms' densities, which are found in the majority in their ground state, is of fundamental importance to describe the kinetics of this medium. In order to detect atoms in the ground state, the most interesting technique is laser induced fluorescence (LIF), where the fluorescence induced by the laser is related to the ground state atoms' density [6]. Although the technique is very attractive, its application in industrial environments is quite complicated, due to the complexity of the laser systems.…”

Section: Introductionmentioning

confidence: 99%

Validity of actinometry to measure N and H atom concentration in N₂-H₂direct current glow discharges

Thomaz

Amorim

Souza

1999

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

Abstract. The validity of actinometry to measure N and H atoms in nitrogen-hydrogen direct current (dc) glow discharges was investigated. The experiments were conducted in positive columns of dc glow discharges, in mixtures of N 2 -xH 2 , where x varies from zero to one, pressures between 133.33 and 533.32 Pa and discharge currents from 1 to 50 mA. The electric fields were measured by electric probes (17 V cm −1 < E < 32 V cm −1 ), and the gas temperatures (490 K < T g < 910 K) were deduced from the rotational transitions of molecular-band systems. The actinometry was performed using argon as the actinometer gas and compared with laser induced fluorescence measurements of ground-state atoms, in order to establish the limits of the validity of actinometry. A theoretical approach was used in order to interpret the behaviour of the emission lines. In nitrogen-hydrogen positive columns, the actinometry method indicated the correct behaviour of the N atoms density in the range of zero to one for x and for H atoms in the region from x = 0 to x = 0.2.

show abstract

Production and Detection of H Atoms and Vibrationally Excited H₂ Molecules in CVD Processes

Umemoto¹

2010

Chemical Vapor Deposition

View full text Add to dashboard Cite

Radical species, including atomic hydrogen, play an important role in the CVD process to prepare high-quality thin solid films. Detailed information on the absolute densities of these radicals under various conditions is needed in order to understand the chemical kinetics involved and to control the deposition processes. This article reviews the production mechanisms and the gasphase diagnostic techniques for H atoms in catalytic CVD (also called hot-wire CVD) and plasma-enhanced (PE)CVD processes. Experimentally determined absolute H-atom densities in typical CVD processes are compiled in a table. Under suitable conditions, the steady-state H-atom density can be increased up to 10 17 cm À3. Procedures for producing and detecting vibrationally excited H 2 molecules, which can be another active species in CVD processes, are also discussed.

show abstract

Two-photon laser induced fluorescence and amplified spontaneous emission atom concentration measurements in O2 and H2 discharges

Cited by 71 publications

References 29 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

Validity of actinometry to measure N and H atom concentration in N₂-H₂direct current glow discharges

Production and Detection of H Atoms and Vibrationally Excited H₂ Molecules in CVD Processes

Contact Info

Product

Resources

About

Two-photon laser induced fluorescence and amplified spontaneous emission atom concentration measurements in O2 and H2 discharges

Cited by 71 publications

References 29 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

Validity of actinometry to measure N and H atom concentration in N2-H2direct current glow discharges

Production and Detection of H Atoms and Vibrationally Excited H2 Molecules in CVD Processes

Contact Info

Product

Resources

About

Validity of actinometry to measure N and H atom concentration in N₂-H₂direct current glow discharges

Production and Detection of H Atoms and Vibrationally Excited H₂ Molecules in CVD Processes