Highly AccurateH2Lyman and Werner Band Laboratory Measurements and an Improved Constraint on a Cosmological Variation of the Proton-to-Electron Mass Ratio

Transition wavelengths on a large set of H₂ Lyman and Werner band spectral lines have been obtained at an accuracy of 5×10^-8, using a narrow band tunable extreme ultraviolet laser. The data are used to determine a constraint on a possible cosmological variation of the proton-to-electron mass ratio (μ=Mₚ/mₑ) from a comparison with highly redshifted spectral data of quasistellar objects, yielding a fractional change in the mass ratio of Δμ/μ=-0.5±3.6×10^-5 (2σ), which would correspond to a temporal change of d/dt(Δμ/μ)=-0.4±3.0×10^-15 per year (2σ) if a linear cosmological expansion model is assumed.