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B-spline basis sets are applied to the calculation of dipole matrix elements for the hydrogen atom placed in an intense magnetic field, in view of applications to the spectroscopic analysis of white dwarf atmospheres. A focus is put on the H- α line and magnetic field values in the kilotesla range are considered. The dipole matrix elements are shown to be significantly sensitive to the magnetic field. In the framework of plasma diagnostic, this means that the Stark broadening of the line, which is involved in density measurements, can be misinterpreted if the atomic structure is not well accounted for in numerical codes. As an illustration, we consider the H- α σ − component and apply a computer simulation method to the modeling of the Stark broadening of this line. The calculated dipole matrix elements are used therein as input. • B-spline basis sets are applied to the calculation of dipole matrix elements for the hydrogen atom placed in an intense magnetic field. • The dipole matrix elements are shown to be significantly sensitive to the quadratic Zeeman effect. • A discussion of this result is done in view of applications to the spectroscopic analysis of magnetic white dwarf atmospheres. [ABSTRACT FROM AUTHOR]

In plasmas subject to a strong magnetic field, the dynamical properties of the microfield are affected by the cyclotron motion, which can alter Stark-broadened lines. We illustrate this effect through calculations of the hydrogen Lyman a line in an ideal one-component plasma. A focus is put on the central Zeeman component. It is shown that the atomic dipole autocorrelation function decreases more slowly if the cyclotron motion is retained. In the frequency domain, this denotes a reduction of the line broadening. A discussion based on numerical simulations and analytical estimates is done. [ABSTRACT FROM AUTHOR]

Stochastic processes may be used as an efficient model for the line shapes affected by Stark effect in edge plasma conditions. We check the accuracy of this approach on the Lyman γ line of hydrogen perturbed by ions only. We also use a stochastic process to investigate the effect of plasma oscillations on a line shape. Our model assumes that Langmuir waves are a sequence of oscillating electric fields changing their amplitude and phase according to an exponential waiting time distribution. The possible effects of Langmuir waves on the Lyman α Stark profile are discussed in edge plasma conditions. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

• The Stark broadening of hydrogen lines is reexamined in the case of plasmas subject to a large external magnetic field. • It is shown that the energy degeneracy removal due to the diamagnetic Zeeman effect strongly affect the line broadening. • Computer simulations of Lyman and Balmer line shapes in white dwarf atmosphere conditions are performed as an illustration. The Stark broadening of hydrogen lines with a low upper principal quantum number n is reexamined in the case of plasmas subject to a large (≳ 1 kT) external magnetic field. This investigation has been motivated by the observation of strong Zeeman splitting in a significant number of white dwarf spectra. The diamagnetic Zeeman effect term present in the Hamiltonian removes the degeneracy of the energy levels in orbital quantum number l , which results in an alteration of the Stark perturbation due to the microfield. In this work, we investigate this effect by applying a computer simulation method designed for Stark broadening modeling. A focus is put on the Lyman α and H- α lines. Based on line shape calculations, we show that the width of the Zeeman components is strongly dependent on the magnetic field. [ABSTRACT FROM AUTHOR]

An investigation of spectral line broadening in plasmas is carried out within a kinetic-theory approach, based on the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. The model employs a resummation procedure to account for correlated emitter-perturber collisions. Applications to hydrogen lines indicate that such collisions strongly affect the width and the shape in the core region. This argument is supported by comparisons to numerical simulations. It is also shown that the usual collision operator models, based on a binary description of emitter-perturber collisions, can be extremely inaccurate. The present model, in a better agreement with numerical simulations, is suggested as an extension suitable for the design of fast and accurate numerical routines for plasma diagnostics. [ABSTRACT FROM AUTHOR]

The impact approximation used in the modelling of Stark profiles is examined when a magnetic field is present. Motivated by tokamak plasma spectroscopy, we calculate line shapes and S-matrix elements for the first Lyman lines of hydrogen with two models proposed for retaining simultaneously Stark and Zeeman effects in the impact limit. An evaluation of the accuracy of the two approaches is made with the help of a numerical simulation. [ABSTRACT FROM AUTHOR]