arXiv subjects

H. Abgrall

Publications and source records attributed to H. Abgrall.

4 recordsLinked to original sources

arXiv2022

The quasi bound spectrum of H2

We compute the radiative ro-vibrational emission spectrum of H2 involving quasibound states via a simple numerical method of resolution of the Schrödinger equation by introducing a modifed effective molecular potential. The comparison of the eigenvalues obtained with our approximation and other theoretical methods based on scattering resonance properties is excellent. Electric quadrupole and magnetic dipole contributions are calculated and we confirm the previous computations of Forrey of the electric quadrupole transition Einstein coeffcients. The astrophysical relevance of such quasibound levels is emphasized

astro-ph.GA↗

arXiv2019

The full infrared spectrum of molecular hydrogen

The high spectral resolution R about 45,000 provided by IGRINS (Immersion Grating INfrared Spectrometer) at MacDonald Observatory and R 100,000 achieved by CRIRES (CRyogenic high-resolution InfraRed Echelle Spectrograph) at VLT (Very Large Telescope) challenges the present knowledge of infrared spectra. aims We aim to predict the full infrared spectrum of molecular hydrogen at a comparable accuracy. methods We take advantage of the recent theoretical ab initio studies on molecular hydrogen to compute both the electric quadrupole and magnetic dipole transitions taking place within the ground electronic molecular state of hydrogen. results We computed the full infrared spectrum of molecular hydrogen at an unprecedented accuracy and derive for the first time the emission probabilities including both electric quadrupole ($ΔJ = 0, \pm$2) and magnetic dipole transitions ($ΔJ = 0$) as well as the total radiative lifetime of each rovibrational state. Inclusion of magnetic dipole transitions increases the emission probabilities by factors of a few for highly excited rotational levels, which occur in the 3-20 $μ$ range}

physics.atom-ph↗

arXiv2019

H$_2$/HD molecular data for analysis of quasar spectra in search of varying constants

Absorption lines of H$_2$ and HD molecules observed at high redshift in the line of sight towards quasars are a test ground to search for variation of the proton-to-electron mass ratio $μ$. For this purpose, results from astronomical observations are compared with a compilation of molecular data of the highest accuracy, obtained in laboratory studies as well as in first-principles calculations. Aims: A comprehensive line list is compiled for H$_2$ and HD absorption lines in the Lyman ($B^1Σ_u^+$ - $X^1Σ_g^+$) and Werner ($C^1Π_u$ - $X^1Σ_g^+$) band systems up to the Lyman cutoff at 912 Angstroms. Molecular parameters listed for each line $i$ are the transition wavelength $λ_i$, the line oscillator strength $f_i$, the radiative damping parameter of the excited state $Γ_i$, and the sensitivity coefficient $K_i$ for a variation of the proton-to-electron mass ratio. Methods: The transition wavelengths $λ_i$ for the H$_2$ and HD molecules are determined by a variety of advanced high-precision spectroscopic experiments involving narrowband vacuum ultraviolet lasers, Fourier-transform spectrometers, and synchrotron radiation sources. Results for the line oscillator strengths $f_i$, damping parameters $Γ_i$, and sensitivity coefficients $K_i$ are obtained in theoretical quantum chemical calculations. Results: A new list of molecular data is compiled for future analyses of cold clouds of hydrogen absorbers, specifically for studies of $μ$-variation from quasar data. The list is applied in a refit of quasar absorption spectra of B0642$-$5038 and J1237$+$0647 yielding constraints on a variation of the proton-to-electron mass ratio $Δμ/μ$ consistent with previous analyses.

astro-ph.CO↗

arXiv2014

H$_2$ Lyman and Werner band lines and their sensitivity for a variation of the proton-electron mass ratio in the gravitational potential of white dwarfs

Recently an accurate analysis of absorption spectra of molecular hydrogen, observed with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, in the photosphere of white dwarf stars GD133 and GD29-38 was published in a Letter [Phys. Rev. Lett. 113, 123002 (2014)], yielding a constraint on a possible dependence of the proton-electron mass ratio on a gravitational field of strength 10,000 times that at the Earth's surface. In the present paper further details of that study are presented, in particular a re-evaluation of the spectrum of the $B^1Σ_u^+ - X^1Σ_g^+ (v',v'')$ Lyman bands relevant for the prevailing temperatures (12,000 - 14,000 K) of the photospheres. An emphasis is on the calculation of so-called $K_i$-coefficients, that represent the sensitivity of each individual line to a possible change in the proton-electron mass ratio. Such calculations were performed by semi-empirical methods and by ab initio methods providing accurate and consistent values. A full listing is provided for the molecular physics data on the Lyman bands (wavelengths $λ_i$, line oscillator strengths $f_i$, radiative damping rates $Γ_i$, and sensitivity coefficients $K_i$) as required for the analyses of H$_2$-spectra in hot dwarf stars. A similar listing of the molecular physics parameters for the $C^1Π_u - X^1Σ_g^+ (v',v'')$ Werner bands is provided for future use in the analysis of white dwarf spectra.

physics.atom-ph↗