H ₂ /HD molecular data for analysis of quasar spectra in search of varying constants

Context. 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 ¹ Σ _u ⁺ - X ¹ Σ _g ⁺ ) and Werner (C ¹ Π _u - X ¹ Σ _g ⁺ ) band systems up to the Lyman cutoff at 912 Å. 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.