Line positions and strengths in the H2 quadrupole spectrum

Bragg, S. L.; Brault, J. W.; Smith, W. H.

doi:10.1086/160568

Cited by 164 publications

(100 citation statements)

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“…Its frequency is determined at 12 265.5831 ± 0.0007 cm À1 , however at a pressure of 2.8 Bar, while the pressure shift for this transition has not yet been detailed [151]. Assuming a rate-of-change of l À1 (dl/dt) = À2 · 10 À15 yr À1 , also holding in the modern epoch, a K value of 0.46 would correspond to a line drift of 0.34 Hz per year.…”

Section: Possibility Of Laboratory Detection Of L-variation Via H 2 Qmentioning

confidence: 98%

“…The S 3 (1) line in the second vibrational overtone has a cross section of 4.5 · 10 À28 cm/molecule, and is a factor of 80 weaker than the S 1 (1) fundamental vibration [151]. Detection of frequency shifts of H 2 lines of 0.3 Hz are currently outside the realm of feasibility, although laser sources and calibration procedures may soon reach this accuracy.…”

Section: Possibility Of Laboratory Detection Of L-variation Via H 2 Qmentioning

confidence: 99%

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On a possible variation of the proton-to-electron mass ratio: H2 spectra in the line of sight of high-redshift quasars and in the laboratory

Ubachs

Buning

Eikema

et al. 2007

Journal of Molecular Spectroscopy

124

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Recently the finding of an indication for a decrease of the proton-to-electron mass ratio l = m p /m e by 0.002% in the past 12 billion years was reported in the form of a Letter [E. Reinhold, R. Buning, U. Hollenstein, P. Petitjean, A. Ivanchik, W. Ubachs, Phys. Rev. Lett. 96 (2006) 151101]. Here we will further detail the methods that led to that result and put it in perspective. Laser spectroscopy on molecular hydrogen, using a narrow-band and tunable extreme ultraviolet laser system at the Laser Centre Vrije Universiteit Amsterdam, results in transition wavelengths of spectral lines in theWerner band systems at an accuracy of (4-11) · 10 À8, depending on the wavelength region. This corresponds to an absolute accuracy of 0.000004-0.000010 nm. A database of 233 accurately calibrated H 2 lines is presented here for future reference and comparison with astronomical observations. Recent observations of the same spectroscopic features in cold hydrogen clouds at redshifts z = 2.5947325 and z = 3.0248970 in the line of sight of two quasar light sources (Q 0405À443 and Q 0347À383) resulted in 76 reliably determined transition wavelengths of H 2 lines at accuracies in the range 2 · 10 À7 to 1 · 10 À6 . Those observations were performed with the Ultraviolet and Visible Echelle Spectrograph at the Very Large Telescope of the European Southern Observatory at Paranal, Chile. A third ingredient in the analysis is the calculation of an improved set of sensitivity coefficients K i , a parameter associated with each spectral line, representing the dependence of the transition wavelength on a possible variation of the proton-to-electron mass ratio l. The new model for calculation of the K i sensitivity coefficients is based on a Dunham representation of ground state and excited state level energies, derived from the most accurate data available in literature for the X 1 R þ g ground electronic state and the presently determined level energies in the B 1 R þ u and C 1 P u states. Moreover, the model includes adiabatic corrections to electronic energies as well as local perturbation effects between B and C levels. The full analysis and a tabulation of the resulting K i coefficients is given in this paper. A statistical analysis of the data yields an indication for a variation of the proton-to-electron mass ratio of Dl/l = (2.45 ± 0.59) · 10 À5 for a weighted fit and Dl/l = (1.99 ± 0.58) · 10 À5 for an unweighted fit. This result, indicating the decrease of l, has a statistical significance of 3.5r. Mass-variations as discussed relate to inertial or kinematic masses, rather than gravitational masses. Separate treatment of the data gives a similar positive result for each of the quasars Q 0405À443 and Q 0347À383. The statistical analysis is further documented and possible systematic shifts underlying the data, with the possibility of mimicking a non-zero Dl/l value, are discussed. The observed decrease in l corresponds to a rate of change of d lnl/dt = À2 · 10 À15 per year, if a linear variation with time is assumed. Expe...

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Section: Possibility Of Laboratory Detection Of L-variation Via H 2 Qmentioning

confidence: 98%

Section: Possibility Of Laboratory Detection Of L-variation Via H 2 Qmentioning

confidence: 99%

On a possible variation of the proton-to-electron mass ratio: H2 spectra in the line of sight of high-redshift quasars and in the laboratory

Ubachs

Buning

Eikema

et al. 2007

Journal of Molecular Spectroscopy

124

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“…70 Similar value was reported by Kelley and Bragg 71 and is just between other experimental results. 90,91 …”

Section: Appendix B: Autocorrelation Functions For Hard and Soft Collmentioning

confidence: 99%

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

Wcisło

Tran

Kassi

et al. 2014

The Journal of Chemical Physics

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We show how to effectively introduce a proper description of the velocity-changing collisions into the model of isolated molecular transition for the case of self-and Ar-perturbed H 2 . We demonstrate that the billiardball (BB) approximation of the H 2 -H 2 and H 2 -Ar potentials gives an accurate description of the velocitychanging collisions. The BB model results are compared with ab initio classical molecular dynamics simulations (CMDS). It is shown that the BB model correctly reproduces not only the principal properties such as frequencies of velocity-changing collisions or collision kernels, but also other characteristics of H 2 -H 2 and H 2 -Ar gas kinetics like rate of speed-changing collisions. Finally, we present line-shape measurement of Q (1) line of the first overtone band of self-perturbed H 2 . We quantify the systematic errors of line-shape analysis caused by the use of oversimplified description of velocity-changing collisions. These conclusions will have significant impact on recent rapidly developing ultra-accurate metrology based on Doppler-limited spectroscopic measurements like Doppler-width thermometry, atmosphere monitoring, Boltzmann constant determination or transition position and intensity determination for fundamental studies.

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“…Echelle spectra centred on the H 2 (1, 0) S(1) emission line (λ vac = 2.1218334 µm; Bragg et al 1982) were obtained between the 5th and 7th February 1999 (UT) at the UK Infrared Telescope (UKIRT) using the cooled grating spectrometer CGS 4. The instrument was equipped with a 256 × 256 pixel InSb array; the pixel scale was 0 .…”

Section: Position-velocity (P-v) Spectroscopymentioning

confidence: 99%

A near-infrared study of the bow shocks within the L1634 protostellar outflow

O’Connell

Smith

Davis

et al. 2004

A&A

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Abstract. The L1634 bright-rimmed globule contains an intriguing arrangement of shock structures: two series of aligned molecular shock waves associated with the Herbig-Haro flows HH 240 and HH 241. We present near-infrared spectroscopy and narrow-band imaging in the (1, 0) S(1) and (2, 1) S(1) emission lines of molecular hydrogen. These observations yield the spatial distributions of both the molecular excitation and velocity, which demonstrate distinct properties for the individual bow shocks. Bow shock models are applied, varying the shock physics, geometry, speed, density and magnetic field properties to fit two prominent bow shocks. The models predict that both bows move at 60 • to the plane of the sky. High magnetic fields and low molecular fractions are implied. The advancing compact bow HH 240C is interpreted as a J-type bow (frozen-in magnetic field) with the flanks in transition to C-type (field diffusion). It is a paraboloidal bow of speed ∼42 km s −1 entering a medium of quite high density (2 × 10 4 cm −3 ). The following bow HH 240A is faster despite a lower excitation, moving through a lower density medium. We find a C-type bow shock model to fit all the data for HH 240A. The favoured bow models are then tested comprehensively against published H 2 emission line fluxes and CO spectroscopy. We conclude that, while the CO emission originates from cloud gas directly set in motion, the H 2 emission is generated from shocks sweeping through an outflow. Also considering optical data, we arrive at a global outflow model involving episodic slow-precessing twin jets.

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Line positions and strengths in the H2 quadrupole spectrum

Cited by 164 publications

References 0 publications

On a possible variation of the proton-to-electron mass ratio: H2 spectra in the line of sight of high-redshift quasars and in the laboratory

On a possible variation of the proton-to-electron mass ratio: H2 spectra in the line of sight of high-redshift quasars and in the laboratory

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

A near-infrared study of the bow shocks within the L1634 protostellar outflow

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