Crossover from bound to free states in plasmas

Abstract

A self-consistent joint description of free and weakly bound electron states in strongly coupled plasmas is presented. The existence of two problems is emphasized. The first one is a well-known restriction of the number of atomic excited states. Another one is a description of the smooth crossover from bound pair electron-ion excited states to collective excitations of free electrons. The fluctuation approach is developed to study the spectrum domain intermediate between low-lying excited atoms and free electron continuous energy levels. The molecular dynamics method is applied to study the plasma model since the method is able to distinguish all kinds of fluctuations. The electronion interaction is described by the temperature-independent cutoff Coulomb potential. The diagnostics of pair electron-ion fluctuations is developed. The concept of pair fluctuations elucidates the smooth vanishing of atomic states near the ionization limit. The approach suggested removes the artificial break of the electron state density at the ionization limit: atomic state density divergent at the negative energy side and free electron state density starting from zero density at the positive energy side.

Atomistic simulation of laser ablation of gold: Effect of pressure relaxation

“…The adopted model (in contrast to, e.g., that used in [34]) ignores the interaction between electrons and ions. The proposed ETD potential describes only the ion subsystem that is not closed with respect to the electron subsystem, which is not explicitly included into the molecular dynamics model.…”

Experimental study of optical properties of nonideal plasma within the electron concentration range 1017 cm−3 < N e < 1022 cm−3

“…Yet, the spectra of such atoms contain a lot of thickly located lines; resulting from their merge, the optical shift, at sufficiently high den sities, might exceed the value calculated using the Vidal and the Inglis Teller formulas [3]. The Inglis-Teller formula gives values (in modulus) close to the calculation results according to [10,11,14,16]. Within the hydrogen H α line domain, no intensity depression in the same time moments is observed and, thus, is evidence of the high electron concentration on the surface of the plasma channel and of the weak influence of the external envelope consisting of the hydrogen-oxygen plasma on the absorption spectra.…”

“…Within the hydrogen H α line domain, no intensity depression in the same time moments is observed and, thus, is evidence of the high electron concentration on the surface of the plasma channel and of the weak influence of the external envelope consisting of the hydrogen-oxygen plasma on the absorption spectra. Determination of N e according to [10][11][12]14, 16] at ΔЕ = 5 eV gives values from 4 × 10 20 cm -3 to 7 × 10 21 cm -3 , that is, differing by 17 times. The situation at ΔЕ = 0.5 eV is not much better: here, we obtain the electron concentrations from 1.2 × 10 17 cm -3 to 1.8 × 10 18 cm -3 , that is, differing by 15 times.…”

“…In [9][10][11], a formula is given for the boundary of the spectrum of the paired electron ion states in the dense plasma (1) where ΔЕ is given in eV, N e -in cm -3 . This value might be compared to the ΔЕ value considered here because, for bound pairs, bound-bound transitions might be observed.…”

Pressure Fluctuations in Nonideal Plasma

“…It is the area of pair fluctuations. The new result is that there exists area III where there are neither atoms nor pairs [13]. Solid line 3 corresponds to region of concentration n e at T = 5800K where pressure of system does not depend on n e .…”