Collisional ionization and recombination in degenerate plasmas beyond the free-electron-gas approximation

Williams, G.; Fajardo, M.

doi:10.1103/physreve.102.063204

Cited by 4 publications

(3 citation statements)

References 43 publications

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“…Figures 1 and 2 of Ref. [29] confirm that our plasma is in the classical regime and consequently that the free-electron energy distributions (Eqs. ( 10) and ( 16)) are very close.…”

Section: Comparisonsupporting

confidence: 81%

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Ionization by electron impacts and ionization potential depression

Benredjem¹,

Pain²,

Calisti³

et al. 2022

J. Phys. B: At. Mol. Opt. Phys.

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We calculate the cross-section of ionization by free-electron impacts in high or moderate density plasmas. We show that the so-called ionization potential depression (IPD) strongly aﬀects the magnitude of the cross-section in the highdensity domain. We use the well-known IPD formulas of Stewart-Pyatt and Ecker-Kröll. A more recent approach based on classical molecular dynamics simulation is also investigated. The latter provides an alternative way to calculate IPD values. At near-solid densities the eﬀects of the free-electron degeneracy should be investigated. The rates are then calculated within the Fermi-Dirac statistics. We ﬁrst use the semi-empirical formula of Lotz for ionization cross-section. The results may diﬀer signiﬁcantly from measured cross-sections or calculations with reliable atomic codes. Then, in a second step, we propose a new formula that combines the Lotz formula and a polynomial expansion in terms of the ratio of the energy of the incident electron and the ionization energy. The coeﬃcients of the polynomial expansion are adjusted to ﬁt the cross-section provided by robust atomic codes. A great advantage of the new formula is that it allows a fully analytical calculation of the ionization rate. Our results are compared to experiments measuring IPDs, cross-sections and rate coeﬃcients on aluminum at high and moderate densities and on Be-like CNO ions.

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“…Figures 1 and 2 of Ref. [29] confirm that our plasma is in the classical regime and consequently that the free-electron energy distributions (Eqs. ( 10) and ( 16)) are very close.…”

Section: Comparisonsupporting

confidence: 81%

“…The Maxwell-Boltzmann limit is then relevant. Figures 1 and 2 of reference [29] confirm that our plasma is in the classical regime and consequently that the free-electron energy distributions (equations ( 10) and ( 16)) are very close. Free-electron degeneracy therefore plays a very small role on the ionization at the above conditions.…”

Section: Comparisonsupporting

confidence: 75%

Ionization by electron impacts and ionization potential depression

Benredjem¹,

Pain²,

Calisti³

et al. 2022

J. Phys. B: At. Mol. Opt. Phys.

View full text Add to dashboard Cite

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“…Beyond this value up to 800 eV above the Fermi level, the DOS of a free electron gas is used. 22 All electrons with even higher energies, such as photo-electrons created via non-resonant absorption and Auger-electrons from the decay of core-holes, are described in a separate pool of electrons R free without energy resolution, although the total energy of electrons in this pool is tracked by the parameter E free .…”

Section: Modelingmentioning

confidence: 99%

Electron population dynamics in resonant non-linear x-ray absorption in nickel at a free-electron laser

Engel,

Alexander,

Atak

et al. 2023

Structural Dynamics

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Free-electron lasers provide bright, ultrashort, and monochromatic x-ray pulses, enabling novel spectroscopic measurements not only with femtosecond temporal resolution: The high fluence of their x-ray pulses can also easily enter the regime of the non-linear x-ray–matter interaction. Entering this regime necessitates a rigorous analysis and reliable prediction of the relevant non-linear processes for future experiment designs. Here, we show non-linear changes in the L3-edge absorption of metallic nickel thin films, measured with fluences up to 60 J/cm2. We present a simple but predictive rate model that quantitatively describes spectral changes based on the evolution of electronic populations within the pulse duration. Despite its simplicity, the model reaches good agreement with experimental results over more than three orders of magnitude in fluence, while providing a straightforward understanding of the interplay of physical processes driving the non-linear changes. Our findings provide important insights for the design and evaluation of future high-fluence free-electron laser experiments and contribute to the understanding of non-linear electron dynamics in x-ray absorption processes in solids at the femtosecond timescale.

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