A kinetic model for the formation of excimers

Neeser, S.; Kunz, T.; Langhoff, H.

doi:10.1088/0022-3727/30/10/016

Cited by 41 publications

(46 citation statements)

References 43 publications

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“…8,12,13 The processes that lead to the formation and destruction of this species are well known as they are important in the modeling of argon excimer lasers. 14 The presence of Ar 2 + affects the excited states kinetics essentially in two ways: on one hand the three body recombination processes become less important as they are dependent on the population of atomic argon ions Ar + . On the other hand, the dissociative recombination reaction Ar 2 + + e → Ar + Ar͑4s͒ and the associative ionization Ar͑4s͒ + Ar͑4s͒ → Ar 2 + + e of the 4s metastable levels affect the population of the 4s excited levels.…”

Section: Argon Collisional-radiative Modelmentioning

confidence: 99%

Measuring the electron temperature by optical emission spectroscopy in two temperature plasmas at atmospheric pressure: A critical approach

Yanguas‐Gil

Cotrino

González‐Elipe

2006

Journal of Applied Physics

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The measurement of the electron mean kinetic energy by identifying the electron temperature and the excitation temperature obtained by optical emission spectroscopy is theoretically studied for two temperature argon plasmas at atmospheric pressure. Using a 32-level collisional radiative model in which both electron impact and argon-impact inelastic collisions are taken into account, it has been found that under certain conditions the argon inelastic collisions may cause a decrease of the argon excitation temperature so that the relation T e Ͼ T exc Ͼ T 0 is satisfied. This inequality also appears when electron losses due to diffusion are important and the electron density is lower than its equilibrium value.

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Section: Argon Collisional-radiative Modelmentioning

confidence: 99%

Measuring the electron temperature by optical emission spectroscopy in two temperature plasmas at atmospheric pressure: A critical approach

Yanguas‐Gil

Cotrino

González‐Elipe

2006

Journal of Applied Physics

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“…The radiative deexcitations coefficients are of extreme importance because the power emitted in this way will reach the attenuator walls without heating either the electrons or the gas. The lifetime of the Ar p effective level has been taken directly from the literature (Wiese & Martin, 1980), as well as for the Ar Ã 2 excimer state (Neeser et al, 1997). However, for the Ar s states the mixture between resonant and metastable states at high pressure requires taking into account the exchange between levels due to electron collisions (Carbone et al, 2013) (1997) photons (Mills & Hieftje, 1984).…”

Section: Fluid Modelmentioning

confidence: 99%

Hybrid modelling of a high-power X-ray attenuator plasma

Ortega

Lacoste

Minea

2018

J Synchrotron Radiat

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X-ray gas attenuators act as stress-free high-pass filters for synchrotron and free-electron laser beamlines to reduce the heat load in downstream optical elements without affecting other properties of the X-ray beam. The absorption of the X-ray beam triggers a cascade of processes that ionize and heat up the gas locally, changing its density and therefore the X-ray absorption. Aiming to understand and predict the behaviour of the gas attenuator in terms of efficiency versus gas pressure, a hybrid model has been developed, combining three approaches: an analytical description of the X-ray absorption; Monte Carlo for the electron thermalization; and a fluid treatment for the electron diffusion, recombination and excited-states relaxation. The model was applied to an argon-filled attenuator prototype built and tested at the European Synchrotron Radiation Facility, at a pressure of 200 mbar and assuming stationary conditions. The results of the model showed that the electron population thermalizes within a few nanoseconds after the X-ray pulse arrival and it occurs just around the X-ray beam path, recombining in the bulk of the gas rather than diffusing to the attenuator walls. The gas temperature along the beam path reached 850 K for 770 W of incident power and 182 W m of absorbed power. Around 70% of the absorbed power is released as visible and UV radiation rather than as heat to the gas. Comparison of the power absorption with the experiment showed an overall agreement both with the plasma radial profile and power absorption trend, the latter within an error smaller than 20%. This model can be used for the design and operation of synchrotron gas attenuators and as a base for a time-dependent model for free-electron laser attenuators.

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“…Up to 25 meV/atom of pumping energy was deposited in the gas. According to the kinetic modelling [13] of the induced reactions, at these conditions a maximum population density of about 5 · 10 15 cm −3 is accomplished for the Ar * 2 (4s 3 Σ u ) state. Also the Ar * 2 (4s 1 Σ u ) state is substantially populated reaching its maximum of about 1 · 10 15 cm −3 at 40 ns after the beginning of the excitation.…”

Section: A) Absorption Spectrometrymentioning

confidence: 99%

“…This allows one to calculate the Franck Condon factors. If it is assumed, that at 30 ns the vibrational temperature is 540 K [13], the relative populations of the radiating states may be evaluated. The resulting relative intensities are listed in Table 1 column 5.…”

Section: A) Absorption Spectrometrymentioning

confidence: 99%

“…These continua may be ascribed to the expected absorption from the Ar * 2 (4s 1 Σ u ) state. This state is populated [13] by the electron induced spin flip reaction from Ar * 2 (4s 3 Σ u ) and has a lifetime of 4 ns [14]. Since it may be assumed, that the rotational and vibrational relaxation processes proceed in a time comparable to the lifetime, the absorption structure appears to be broadened.…”

Section: A) Absorption Spectrometrymentioning

confidence: 99%

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Spectroscopic properties of the Ar*2(5p) excimer states

Kunz

Neeser

Langhoff

1997

Z Phys D - Atoms, Molecules and Clusters

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The transitions between Ar * 2 (5p) and Ar * 2 (4sΣ u ) have been investigated by absorption spectrometry. The fine structure of the Ar * 2 (5p 3 Π g ) was attributed to a predominantly Hund's case a coupling. A spin orbit coupling constant of A = (9.8±0.3) cm −1 results. Absorption by the singlet system allows one to determine the triplet/singlet splitting between the Ar * 2 (4sΣ u ) states to be (540 ± 100) cm −1 . The transition probabilities of the Ar * 2 (5p) and Ar * 2 (6p) levels were determined by saturation spectrometry yielding values between (0.2 − 2.5) · 10 6 s −1 .

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A kinetic model for the formation of excimers

Cited by 41 publications

References 43 publications

Measuring the electron temperature by optical emission spectroscopy in two temperature plasmas at atmospheric pressure: A critical approach

Measuring the electron temperature by optical emission spectroscopy in two temperature plasmas at atmospheric pressure: A critical approach

Hybrid modelling of a high-power X-ray attenuator plasma

Spectroscopic properties of the Ar*2(5p) excimer states

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