HD as a Probe for Detecting Mass Variation on a Cosmological Time Scale

Abstract

The strong electronic absorption systems of the B 1 u ÿ X 1 g Lyman and the C 1 u ÿ X 1 g Werner bands can be used to probe possible mass-variation effects on a cosmological time scale from spectra observed at high redshift, not only in H 2 but also in the second most abundant hydrogen isotopomer HD. High resolution laboratory determination of the most prominent HD lines at extreme ultraviolet wavelengths is performed at an accuracy of = 5 10 ÿ8 , forming a database for comparison with astrophysical data. Sensitivity coefficients K i d ln i =d ln are determined for HD from quantum ab initio calculations as a function of the proton-electron mass ratio . Strategies to deduce possible effects beyond first-order baryon/lepton mass ratio deviations are discussed. DOI: 10.1103/PhysRevLett.100.093007 PACS numbers: 33.20.ÿt, 06.20.Jr, 95.30.Dr, 98.80.Bp The observation of spectral features at high redshift (z 2-3) provides an opportunity to probe minute variations of some fundamental constants over time intervals of 10 10 years, corresponding to 80% of the lifetime of the Universe. For the fine structure constant evidence has been reported for a temporal drift at 5 significance [1]. Variation of another fundamental constant, the dimensionless proton-electron mass ratio m p =m e , may be probed through spectra of molecules. Recently, an indication for a possible decrease of was reported at = 2:45 0:59 10 ÿ5 over a time interval of 12 10 9 years [2,3]. This result is derived from a set of 76 H 2 spectral lines in two absorption systems at z 2:59 and z 3:02 in the line of sight towards quasars Q0405 ÿ 443 and Q0347 ÿ 383 [4]. From observations of the NH 3 inversion splitting in the astrophysical object B0218 357 at z 0:68, a tight constraint upon variation at = 0:6 1:9 10 ÿ6 was deduced [5]. These seemingly contradictory results might be reconciled by invoking the concept of a phase transition having occurred at z 1, transiting from a matter-dominated to a darkenergy-dominated Universe; variation of constants is hypothesized to occur only before the phase transition, henceThe comparison of spectral lines over cosmological time scales depends on the availability of spectral transitions that can be observed at high accuracy and at high redshift. Molecular hydrogen is the most abundant molecule in the Universe by orders of magnitude. The abundance of the deuterated HD species competes with other abundant molecules such as CO and CH such that it is worthwhile to consider the opportunity of using HD absorption for probing mass-variation effects. HD lines in the Lyman bands have indeed been observed in the object Q1232 082 at z 2:34 [7].To facilitate this opportunity, a set of highly accurate zero-redshift (laboratory) transition wavelengths of HD electronic absorption lines is required. Here we report on the spectral calibration of zero-redshift HD lines in the B 1 u ÿ X 1 g Lyman and the C 1 u ÿ X 1 g Werner bands, referred to as Lv and Wv bands with v the vibrational quantum number, in the extreme ultraviolet range 100-11...

Perspective: Tipping the scales: Search for drifting constants from molecular spectra

“…laboratory absorption spectrum of H 2 and HD, including information on the intensities, is made available in digital form in the supplementary material of Ref. 56.…”

“…[52][53][54] Similar investigations of the XUV-laser spectrum of HD were performed in view of the fact that HD lines were also observed in high-redshift spectra towards quasar sources. 55,56 Additional spectroscopic studies of H 2 were performed assessing the level energies in these excited states in an indirect manner, thereby verifying and even improving the transition frequencies in the Lyman and Werner bands. 57,58 The data set of laboratory wavelengths obtained for both H 2 and HD, has reached an accuracy that can be considered exact for the purpose of comparison with quasar data, where accuracies are never better than 10 −7 .…”

Velocity-changing collisions in pure H2 and H2-Ar mixture

“…Clearly, the use of realistic description of collisions in line shape calculations is crucial for different applications such as the spectroscopic determination of the Boltzmann constant, 4,5,46,86 testing quantum treatment of molecules with high precision (in particular, line intensities) 49 or search for new fundamental physical effects. 87,88 Comparing the descriptions of the velocity-changing collisions given by various models (see Sec. V A) and corresponding residua (see Fig.…”

Micro-Kelvin cold molecules.

“…At these low kinetic energies, external electric, magnetic, or optical field can be used to trap, store, and manipulate the molecules, making them ideal targets for studying collisional dynamics, femto/atto-second time resolved spectroscopy, and radical-radical (barrierless) reactions. The ability to confin and control the molecules along with the extended observation times allows for ultra-high resolution spectroscopy that, for example, may enable the direct counting of the density of states of the molecules [2], as well as precision measurements of fundamental physical constants [13,26,11], and even the detection of gravitational waves [32]. By trapping and orienting molecules prior to photo-dissociation, the spatial averaging associated with randomly oriented molecules can be greatly reduced, yielding new details in the observed angular distributions of the photo-fragments that can reveal the underlying dynamics of the photodissociation process [30].…”