International audienceModeling the Stark broadening of spectral lines in plasmas is a complex problem. The problem has a long history, since it plays a crucial role in the interpretation of the observed spectral lines in laboratories and astrophysical plasmas. One difficulty is the characterization of the emitter's environment. Although several models have been proposed over the years, there have been no systematic studies of the results, until now. Here, calculations from stochastic models and numerical simulations are compared for the Atoms 2014, 2 300 Lyman-α and -β lines in neutral hydrogen. Also discussed are results from the Helium-α and -β lines of Ar XVII

Pressure broadening of Lyman-lines of hydrogen-like lithium is studied using a quantum statistical approach to the line shape in dense plasmas. We report line widths (FWHM) and shifts for Lα, L β , and Lγ in a wide range of densities and temperatures relevant for laser-produced lithium plasmas. We estimate the influence of ion dynamics and strong collisions. The results are applied to measured spectra of lithium irradiated by a nanosecond laser pulse of moderate intensities (I ≈ 10 11 − 10 13 W/cm 2 ), see G. Schriever et al. [1,2]. By matching synthetic spectra to the experimental ones, density and temperature conditions are inferred assuming the model of a one-dimensional uniform plasma slab. This allows for a more precise estimate of the density compared to the results reported earlier. Self-absorption is accounted for and found to be important for Lα.

To apply spectroscopy as a diagnostic tool for dense plasmas, a theoretical approach to pressure broadening is indispensable. Here, a quantum-statistical theory is used to calculate spectral line shapes of few-electron atoms. Ionic perturbers are treated quasistatically as well as dynamically via a frequency fluctuation model. Electronic perturbers are treated in the impact approximation. Strong electron-emitter collisions are consistently taken into account with an effective two-particle T-matrix approach. Convergent close-coupling calculations give scattering amplitudes including Debye screening for neutral emitters. For charged emitters, the effect of plasma screening is estimated. The electron densities considered reach up to n(e) = 10(27) m(-3). Temperatures are between T = 10(4) and 10(5) K. The results are compared with a dynamically screened Born approximation for Lyman lines of H and H-like Li as well as for the He 3889 Å line. For the last, a comprehensive comparison to simulations and experiments is given. For the H Lyman-α line, the width and shift are drastically reduced by the Debye screening. In the T-matrix approach, the line shape is notably changed due to the dependence on the magnetic quantum number of the emitter, whereas the difference between spin-scattering channels is negligible.

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Broadening of spectral lines by a plasma surrounding can be used for plasma diagnostics. Full hydrogen Lyman line profiles are calculated with a quantum‐statistical approach. The effects of plasma electrons and ions on the emitter states are considered separately. The influence of electrons is considered in a dynamically screened Born approximation (collision approximation). For the ions, we apply the quasi‐static approximation and two different approaches to account for ion‐dynamics, namely, the model microfield method (MMM) and the frequency fluctuation model (FFM). We compare resulting widths of Lyman lines in the temperature range T = 104 to 107 K and the free electron density range ne = 1023 to 1026 m–3. For Lα, the error made by neglecting ion‐dynamics increases with increasing temperature and decreasing density, and is at least –15%. Due to the double peaked structure of Lβ the situation is less systematic. However, a large region exists, where ion‐dynamics does not affect the line shape of Lβ. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)