Indication of a Cosmological Variation of the Proton-Electron Mass Ratio Based on Laboratory Measurement and Reanalysis of H₂ Spectra

Based on highly accurate laboratory measurements of Lyman bands of H₂ and an updated representation of the structure of the ground X ¹Σ_g⁺ and excited B ¹Σ_u⁺ and C ¹Π_u states, a new set of sensitivity coefficients K_i is derived for all lines in the H₂ spectrum, representing the dependence of their transition wavelengths on a possible variation of the proton-electron mass ratio μ=m_p/m_e. Included are local perturbation effects between B and C levels and adiabatic corrections. The new wavelengths and K_i factors are used to compare with a recent set of highly accurate H₂ spectral lines observed in the Q 0347-383 and Q 0405-443 quasars, yielding a fractional change in the mass ratio of Δμ/μ=(2.4±0.6)×10^-5 for a weighted fit and Δμ/μ=(2.0±0.6)×10^-5 for an unweighted fit. This result indicates, at a 3.5σ confidence level, that μ could have decreased in the past 12 Gyr.