A molecular probe of dark energy

Many theories of dark energy invoke rolling scaler fields which in turn predict time variable fundamental constants such as the ratio of electron to proton mass μ. Molecular energy levels are sensitive to μ with the electronic, vibrational and rotational levels affected each in a different manner depending on their quantum numbers. High redshift damped Lyman alpha clouds with molecular hydrogen offer an excellent opportunity to search for this possible variation. New, very accurate, laboratory measurements of the wavelengths of the Lyman and Werner transitions make it now possible to check whether the small variations in wavelength due to a time varying value of μ, are present.