Improved determination of the B–X and C–X transition wavelengths of molecular hydrogen

Abstract

We present two separate high precision spectroscopies of molecular hydrogen, one in the deep ultraviolet region and the other covering the infrared to visible spectral range. The combined results of the measurements enable an accurate determination of B–X (Lyman) and C–X (Werner) transition wavelengths, that are the most prominent H2 lines used in studies that probe for a possible variation of the proton-toelectron mass ratio (μ = mₚ /mₑ) over cosmological timescales. The accuracy obtained represent more than an order of magnitude improvement over previous determinations involving direct excitation of the Lyman and Werner transitions in the extreme ultraviolet region.