Measurements of population densities of metastable and resonant levels of argon using laser induced fluorescence

Nikolić, Milka; Newton, J.O.; Sukenik, C. I.; Vušković, L.; Popović, S.

doi:10.1063/1.4905611

Cited by 12 publications

(6 citation statements)

References 21 publications

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“…Further emission bands are observed in the longer wavelength regime between 690 nm and 800 nm which can be assigned to the transitions from highly excited argon into metastable states of argon. These are the transitions from the 3p 5 4p level (13 eV) into the 3p 5 4s level (11-12 eV) 38 .…”

Section: Resultsmentioning

confidence: 99%

Development of an inverse low‐temperature plasma ionization source for liquid chromatography/mass spectrometry

Brecht

Uteschil

Schmitz

2021

Rapid Comm Mass Spectrometry

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Section: Resultsmentioning

confidence: 99%

Development of an inverse low‐temperature plasma ionization source for liquid chromatography/mass spectrometry

Brecht

Uteschil

Schmitz

2021

Rapid Comm Mass Spectrometry

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“…In order to model the cathode layer, the secondary electron emission coefficient was taken c ¼ 0.05, as indicated by the best fit to different abnormal glow discharges in argon. 9 Expressions of the ionization Townsend Townsend's coefficient for molecule excitation to metastable level Ar( 3 P 2 ) was taken as that for ionization, 11 corrected for the difference between ionization and excitation energies. Concerning the metastable lifetime, for small extension of the cathode layer (below 10 lm), the results are not sensitive to lifetime values above 1 ls because the exponential inside the integral in Eq.…”

Section: Resultsmentioning

confidence: 99%

Study of a contracted glow in low-frequency plasma-jet discharges operating with argon

et al. 2015

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In this work, we present an experimental and theoretical study of a low frequency, atmospheric plasma-jet discharge in argon. The discharge has the characteristics of a contracted glow with a current channel of submillimeter diameter and a relatively high voltage cathode layer. In order to interpret the measurements, we consider the separate modeling of each region of the discharge: main channel and cathode layer, which must then be properly matched together. The main current channel was modeled, extending a previous work, as similar to an arc in which joule heating is balanced by lateral heat conduction, without thermal equilibrium between electrons and heavy species. The cathode layer model, on the other hand, includes the emission of secondary electrons by ion impact and by additional mechanisms, of which we considered emission due to collision of atoms excited at metastable levels, and field-enhanced thermionic emission (Schottky effect). The comparison of model and experiment indicates that the discharge can be effectively sustained in its contracted form by the secondary electrons emitted by collision of excited argon atoms, whereas thermionic emission is by far insufficient to provide the necessary electrons. V

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“…Several cross‐section data sets are available in the literature and through the online Plasma Data Exchange Project (LXCat) . Paschen notation [ 28 ] is used throughout this study to describe the excited states of argon. Argon plasma models are often simplified by grouping electronic excitation processes though a summed cross‐section.…”

Section: Methodsmentioning

confidence: 99%

Continuum modelling of an asymmetric CCRF argon plasma reactor: Influence of higher excited states and sensitivity to model parameters

Baldry

Haidar

Akhavan

et al. 2021

Plasma Processes & Polymers

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Precise control of capacitively coupled radiofrequency (CCRF) plasma reactors is required to achieve desired outcomes in surface functionalisation and material synthesis processes. This necessitates detailed mapping of the large process parameter space and a thorough understanding of spatial and temporal variations of the plasma throughout the reactor. These goals can only feasibly be achieved with accurate numerical modelling. Previous numerical studies of CCRF discharges have implemented a range of simplifying assumptions to improve numerical tractability, such as small electrode spacing, radial uniformity, fewer active species and simplified boundary conditions, while neglecting self‐bias formation. Although this approach is useful in developing the methodology for continuum plasma modelling, it poses challenges for direct comparison with experimental data and for understanding the behaviour of plasma processes employed in the surface treatment of large, complex objects, or the synthesis of nanoparticles. Here we report the development of a two‐dimensional axisymmetric continuum model for a CCRF reactor with a pure argon 13.56‐MHz discharge using the finite element method. The large electrode spacing and reactor design result in two distinct discharge regions and the formation of a strong DC self‐bias on the powered electrode. The plasma discharge is studied as the pressure is varied from 0.1 to 0.3 Torr, over the radiofrequency input power range of 25–100 W, which leads to consistent enhancements of the electron density and self‐bias. The impact of the electron energy distribution function (EEDF) on the discharge is assessed, with the assumption of a Druyvesteyn EEDF resulting in a bulk electron density and temperature of 3.4 × 1015 m−3 and 3.3 eV, respectively, compared with 8.1 × 1015 m−3 and 1.9 eV in the Maxwellian case. The asymmetric power distribution throughout the reactor is quantified to build a reduced domain model with a lower computational cost. The effect of an electrically floating parallel plate electrode is assessed, resulting in a 42% higher bulk plasma potential as compared with the grounded case. The inclusion of resonant and 2p excited states of argon is shown to have a major impact on the discharge dynamics, leading to an order of magnitude reduction in bulk electron density. This study proposes a robust numerical model of a CCRF argon plasma discharge to facilitate future simulations of more complex discharges with important implications in plasma surface engineering and synthesis of materials.

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Measurements of population densities of metastable and resonant levels of argon using laser induced fluorescence

Cited by 12 publications

References 21 publications

Development of an inverse low‐temperature plasma ionization source for liquid chromatography/mass spectrometry

Development of an inverse low‐temperature plasma ionization source for liquid chromatography/mass spectrometry

Study of a contracted glow in low-frequency plasma-jet discharges operating with argon

Continuum modelling of an asymmetric CCRF argon plasma reactor: Influence of higher excited states and sensitivity to model parameters

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