New study of the quasi-molecular Lyman-γ satellites due to H-H⁺ collisions

Abstract

Context. Quasi-molecular line satellites in the red wings of Lyman series of atomic hydrogen have been identified in the spectra of hydrogen-rich white dwarfs. These features are produced by radiative collisions. Aims. Structures observed about 995 Å in the Lyman-γ wing of hot white dwarfs have been shown to be caused by quasi-molecular absorption of H + 2 molecules. Methods. Improvements to previous theoretical calculations of the Lyman-γ line profiles can be achieved by using a unified theory that takes into account the dependence of the dipole moments on internuclear distance during the collision. Results. For the first time, we have computed the transition dipole moments. We measure a significant increase in the region of the formation of the satellites, which alters the general shape of the profile. Conclusions. A large increase in the strength of the two main satellites at 992 and 996 Å leads to a deeper broad absorption in the synthetic spectra, which should improve the comparison with observation as previous predicted Lyman-γ satellites were too weak.

LiHe spectra from brown dwarfs to helium clusters

“…Consequently, the satellite amplitude will increase as R 2 m . It also depends on the value of the electric dipole transition moment in the internuclear region where the line satellite is formed (Allard et al, 1998). For a transition α = (i, f ) from initial state i to final state f , we definedd ee ′ (R(t)) as a modulated dipole (Eq.…”

Theoretical study of the line profiles of the hydrogen perturbed by collisions with protons

“…The values of the dipole moments of H + 2 that are available in the literature were calculated by Ramaker & Peek (1972, 1973), and Allard, Noselidze & Kruk (2009) refers to the calculation of n = 4.…”

“…The unified theory has been developed in Allard et al (1999), and a detailed discussion is presented there. The fundamental expression of the normalized spectrum line F ν (Δν) is computed from the Fourier transform (Allard et al 2009) …”

Unified line profiles for hydrogen perturbed by collisions with protons: satellites and asymmetries

“…Models were evaluated by , assuming constant dipole moments, and Allard, Noselidze & Kruk (2009), considering their dependence with distance.…”

“…Allard, Noselidze & Kruk 2009). For the other lines of the Lyman series and the Balmer series, the interaction between hydrogen atom and free protons is approximated simply as electron Stark effect, which causes only a broadening that adds up to the effect of the electrons.…”