2019A&A...622A.127U

Context. Absorption lines of H₂ 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 H₂ and HD absorption lines in the Lyman (B¹Σ_u⁺ - X¹Σ_g⁺) and Werner (C¹Π_u - X¹Σ_g⁺) band systems up to the Lyman cutoff at 912Å. 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 H₂ 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.