title: Improved laboratory values of the H2 Lyman and Werner lines for constraining time variation of the proton-to-electron mass ratio.
abstract: Two distinct high-accuracy laboratory spectroscopic investigations of the H2 molecule are reported. Anchor lines in the EF1Sigmag+-X1Sigmag+ system are calibrated by two-photon deep-UV Doppler-free spectroscopy, while independent Fourier-transform spectroscopic measurements are performed that yield accurate spacings in the B1Sigmau+-EF1Sigmag+ and I1Pig-C1Piu systems. From combination differences accurate transition wavelengths for the B-X Lyman and the C-X Werner lines can be determined with accuracies better than approximately 5 x 10(-9), representing a major improvement over existing values. This metrology provides a practically exact database to extract a possible variation of the proton-to-electron mass ratio based on H2 lines in high-redshift objects. Moreover, it forms a rationale for equipping a future class of telescopes, carrying 30-40 m dishes, with novel spectrometers of higher resolving powers.
authors.affiliation: Laser Centre, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
authors.forename: E J
authors.initials: EJ
authors.lastname: Salumbides
authors.forename: D
authors.initials: D
authors.lastname: Bailly
authors.forename: A
authors.initials: A
authors.lastname: Khramov
authors.forename: A L
authors.initials: AL
authors.lastname: Wolf
authors.forename: K S E
authors.initials: KS
authors.lastname: Eikema
authors.forename: M
authors.initials: M
authors.lastname: Vervloet
authors.forename: W
authors.initials: W
authors.lastname: Ubachs