Abstract
Stark-broadened lines of the hydrogen Brackett series are computed for the conditions of stellar atmospheres and circumstellar envelopes. The computation is performed within the Model Microfield Method, which includes the ion dynamic effects and makes the bridge between the impact limit at low density and the static limit at high density and in the line wings. The computation gives the area normalized line shape, from the line core up to the static line wings.
Highlights
Hydrogen is the most abundant element in the universe
Its broad lines give noticeable features in the spectra of stellar atmospheres [1,2,3,4]. These lines are very sensitive to the interaction between hydrogen radiating atoms and the surrounding charges, electrons, and ions, which is connected to the random electric field generated by these charges
This paper aims at providing a coherent description of the line shapes of Brackett α, β, γ, which connect the levels of principal quantum numbers n equal to 4, for the lower state of the transition, and n equal to 5, 6, and 7, for the upper state, and have central wavelengths of 4.05, 2.63, and 2.12 μm
Summary
Hydrogen is the most abundant element in the universe. Its broad lines give noticeable features in the spectra of stellar atmospheres [1,2,3,4]. These lines are very sensitive to the interaction between hydrogen radiating atoms and the surrounding charges, electrons, and ions (mostly protons), which is connected to the random electric field generated by these charges. The electric field has two components, with different time scales: the rapidly varying electronic field and the slowly varying ionic electric field. The net field induces a strong mixing of the atomic states with the same principal quantum number, from which the Stark broadening originates. Astrophysical applications need to know the full line shape, from line centre up to the line wings, for a wide range of plasma conditions (i.e., electron density Ne and temperature T)
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