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

Abstract

Transition wavelengths on a large set of H 2 Lyman and Werner band spectral lines have been obtained at an accuracy of 5 10 ÿ8 , 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 ( M p =m e ) from a comparison with highly redshifted spectral data of quasistellar objects, yielding a fractional change in the mass ratio of = ÿ0:5 3:6 10 ÿ5 (2 ), which would correspond to a temporal change of d=dt = ÿ0:4 3:0 10 ÿ15 per year (2 ) if a linear cosmological expansion model is assumed. DOI: 10.1103/PhysRevLett.92.101302 PACS numbers: 98.80.Es, 14.20.Dh, 33.20.Ni, 98.62.Ra The search for a cosmological variability of fundamental physical constants has become an active field of research now that accurate spectroscopic data can be obtained from quasars that have emitted their radiation more than ten billion years ago. A comparison between laboratory data, obtained at the highest accuracy in the modern epoch, and analysis of corresponding redshifted spectra from distant objects allows for stringent constraints on variability of the physical constants underlying the spectra. One such issue is that of the fine structure constant , which was claimed to vary based on observations of quasar spectra [1]. Another is that of the proton-to-electron mass ratio M p =m e , a dimensionless parameter equalling 1836.152 672 61(85) [2]. The idea that fundamental physical constants might not be constant on a cosmological time scale was pioneered by Dirac, Teller, Gamov, and others; the observational status and theoretical perspectives were recently discussed by Uzan [3], citing all relevant publications.The spectrum of molecular hydrogen with the prominent Lyman and Werner band systems may be used to detect a change in over time, because each individual spectral line depends in a different way on the mass ratio, as was pointed out by Thompson [4]. In recent years, several observations have been made on the Lyman and Werner bands in quasars, taking advantage of the fact that Earth's atmosphere is transparent for these spectral regions at high z, and that ground-based echelle-grating spectrometers can be employed in high-resolution studies [5][6][7][8][9][10]. In comparisons, the laboratory data of the Lyman and Werner band tables of the Meudon group were used [11,12], which represent an extensive and accurate database. Nevertheless, it was emphasized that improved spectroscopic data are desired [8], because the statistical errors from astronomical and laboratory data contributed equally in the estimates of = , the fractional variation of . This is illustrated by the fact that Ivanchik et al. [8] find rather different constraints on = , when comparing quasar data with different laboratory data sets [11][12][13]. Here we report on laser-based laboratory determinations of Lyman and Werner band spectral lines at an accuracy improved by more than an order of magnitude; the resulting laboratory wavelengths 0 i can be consid...

Frequency-mixing scheme for the production of tunable narrowband XUV radiation (91–95 nm): application to precision spectroscopy and predissociation in diatomic molecules

“…At temperatures of 10 K the FWHM-Doppler width of the H 2 lines is 4.5 GHz; this may be compared with the width (0.55 GHz) and accuracy (<0.3 GHz) obtained in the present laboratory investigation. Finally, the present data may be implemented in improved comparisons between laboratory data and observed spectra from distant quasars, thus revealing pos- sible cosmological variations of the proton-to-electron mass ratio (39)(40)(41).…”

Cosmological constraints on a dynamical electron mass

“…The observational constraints from redshifts of order 1 [1,2,3] therefore convert into a bound on ω the one free parameter defining the theory and…”

“…This work is motivated by recent observational constraints [1,2,3] on variations of the electron-proton mass ratio µ = m e /m p which take advantage of new high-precision spectra to complement previous investigations of µ in combination with the fine structure constant, α, and the proton g-factor, g p , [4,5,6]. It is important to relate these constraints to independent investigations on varying α [7,8,9].…”

Partial covering of the emission regions of Q 0528−250 by intervening H2 clouds

“…(i) The discovery of HD/H2 clouds at high redshift (Varshalovich et al 2001) provides an independent way to estimate the primordial deuterium abundance (D/H) and therefore the relative baryon density of the Universe Ω b which is one of the key cosmological parameters Ivanchik et al 2010). (ii) The comparison of H2 wavelengths observed in QSO spectra with laboratory ones (just for this quasar Q 0528−250, Varshalovich & Levshakov (1993), Cowie & Songaila (1995), Potekhin et al (1998), Ubachs & Reinhold (2004), King et al (2011)) allows us to test the possible cosmological variation of the proton-toelectron mass ratio µ = mp/me. Because the de-composition of H2 absorptions into several components is crucial for studies of the fundamental constant variability problem, we should pay attention to the partial coverage effect.…”