Hydrogen spectral lines with the inclusion of dense-plasma effects

Abstract

Line profiles for hydrogen including the case of dense plasmas are investigated on the basis of a many-particle approach. Using a Green s-function technique, electron contributions to the shift and broadening from both separate-level and interferencelike terms are considered consistently. The theoretical approach to the line profile has been improved by including dynamic screening of collisions, contributions from hn =0 transitions, and cross-term contributions not only to the broadening but also to the shift of the line. As an example, the line profile of H has been considered. An analysis of details of the second-order approximation with respect to the atom-plasma interaction is given, avoiding the noquenching and dipole approximations. The effect of dynamic screening for high electron densities is investigated. Deviations from the linear dependence between the electron-shift contribution and the density are expected for H for n, &2X10" cm at temperatures of about 10000 K. PACS number(s): 52.25.Rv, 32.70.Jz I. INTRODUCTIGN

Net emission of Ar–H2–He thermal plasmas at atmospheric pressure

“…The Stark broadening is mainly due to the ions, its form is linear and the resulting shape is more complex than a Lorentzian profile when the dynamics of the ions is considered. Several approaches were developed to characterize the shape of the spectral lines: the microfield method that includes the dynamics of the ions and the rotation of the ionic field in the total profile [68][69][70]; the generalized impact theory and the unified classical path theory which are considered as better methods to calculate the hydrogen shapes [12][13][14][15][16]71]; the quantum statistical approach based on the many-particle Green functions method used by Günter [72] and developed for charged perturbers and applied to plasmas as hydrogen [72,74] or helium [74,75]. The normalized profile used in calculation is deduced from works of Vidal, Copper and Smith [ 12,[14][15][16] who c onsidered the unified theory and the impact approximation at the centre of the line and the quasi-static approximation on the edges.…”

Spectral Line Shapes of He I Line 3889 Å

“…Perturbation of the radiating atom or ion by the surrounding particles leads to spectral line broadening (Stark broadening), while the coherent emission process is interrupted by collisions and influenced by plasma microfield. Several theoretical approaches have been applied to calculate Stark broadening, such as the well known semiclassical approximation the standard theory (ST) by Griem [1], or the quantum statistical approach of many-particle theory [2], where the motion of ion perturber is neglected during the inverse halfwidth of the line. Furthermore, the model microfield method (MMM) [3][4][5][6], the frequency fluctuation method (FFM) [7] or computer simulations [8][9][10][11] are used for calculating the line broadening including ion-dynamics effects, which lead to further broadening of the line shapes.…”

Neutral helium spectral lines in dense plasmas

“…In lowest order, they are determined by the atomic eigenfunctions ψ n (P) of the radiating electron and depend on the momentum transferhq [56,61],…”

“…A quantum statistical approach has been developed to account in a systematic way for medium modifications of spectral line shapes [56,61,62]. It starts from the relation of the absorption coefficient α(ω) and the refraction index n(ω) to the dielectric function ǫ(q, ω) in the long wavelength limit q → 0 ,…”

“…Recently, a quantum statistical many body approach taking into account medium effects by using thermodynamic Green function technique has been developed [56,57]. In principle this approach is able to describe dynamical screening and strong collisions by electrons, as well as the dynamic ion microfield in a systematic way.…”