Indication of a Cosmological Variation of the Proton-Electron Mass Ratio Based on Laboratory Measurement and Reanalysis of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi mathvariant="normal">H</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>Spectra

Reinhold, E.M.; Buning, R.; Hollenstein, U.; Ivanchik, A. V.; Petitjean, P.; Ubachs, Wim

doi:10.1103/physrevlett.96.151101

Cited by 285 publications

(362 citation statements)

References 21 publications

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“…5 The most stringent laboratory test of m-variation is set by comparing vibrational transitions in SF 6 with a caesium fountain over 2 years, which has Table 1 Frequencies of selected 2-photon transitions in the a 3 P state of (different isotopomers of) CO together with their sensitivity to a m-variation…”

Section: A Proposed Experiments In Metastable Comentioning

confidence: 99%

Testing the time-invariance of fundamental constants using microwave spectroscopy on cold diatomic radicals

Bethlem

Ubachs

2009

Faraday Discuss.

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The recently demonstrated methods to cool and manipulate neutral molecules offer new possibilities for precision tests of fundamental physics theories. We here discuss the possibility of testing the time-invariance of fundamental constants using near degeneracies between rotational levels in the fine structure ladders of molecular radicals. We show that such a degeneracy occurs between the J ¼ 6, U ¼ 1 and the J ¼ 8, U ¼ 0 levels of the various natural isotopomers of carbon monoxide in its a 3 P state. As a result, the 2-photon transition that connects these states is 300 times more sensitive to a variation of m p /m e than a pure rotational transition. We present a molecular beam apparatus that might be used to measure these transitions with a fractional accuracy of 10 À12 . Ultimately, the precision of an experiment on metastable CO will be limited by the lifetime of the a 3 P state. We will discuss other possible molecules that have a suitable level structure and can be cooled using one of the existing methods.

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Section: A Proposed Experiments In Metastable Comentioning

confidence: 99%

Testing the time-invariance of fundamental constants using microwave spectroscopy on cold diatomic radicals

Bethlem

Ubachs

2009

Faraday Discuss.

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“…To date, studies focusing specifically on potential variations of μ are rare, yielding 1σ confidence levels of order Δμ/μ ∼ 10 −5 Ivanchik et al 2005;Reinhold et al 2006;King et al 2008). Different powers of μ define the scales of electronic, vibrational, and rotational intervals in molecular spectra so that ro-vibronic transitions of the H 2 molecule, observed toward distant quasars, could be used.…”

Section: Article Published By Edp Sciencesmentioning

confidence: 99%

The density, the cosmic microwave background, and the proton-to-electron mass ratio in a cloud at redshift 0.9

Henkel¹,

Menten²,

Murphy

et al. 2009

A&A

151

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Based on measurements with the Effelsberg 100-m telescope, a multi-line study of molecular species is presented toward the gravitational lens system PKS 1830-211, which is by far the best known target to study dense cool gas in absorption at intermediate redshift.Determining average radial velocities and performing Large Velocity Gradient radiative transfer calculations, the aims of this study are (1) to determine the density of the gas, (2) to constrain the temperature of the cosmic microwave background (CMB), and (3) to evaluate the proton-to-electron mass ratio at redshift z ∼ 0.89. Analyzing data from six rotational HC 3 N transitions (this includes the J = 7 ← 6 line, which is likely detected for the first time in the interstellar medium) we obtain n(H 2 ) ∼ 2600 cm −3 for the gas density of the south-western absorption component, assuming a background source covering factor, which is independent of frequency. With a possibly more realistic frequency dependence proportional to ν 0.5 (the maximal exponent permitted by observational boundary conditions), n(H 2 ) ∼ 1700 cm −3 . Again toward the south-western source, excitation temperatures of molecular species with optically thin lines and higher rotational constants are, on average, consistent with the expected temperature of the cosmic microwave background, T CMB = 5.14 K. However, individually, there is a surprisingly large scatter which far surpasses expected uncertainties. A comparison of CS J = 1 ← 0 and 4 ← 3 optical depths toward the weaker north-western absorption component results in T ex = 11 K and a 1-σ error of 3 K. For the main component, a comparison of velocities determined from ten optically thin NH 3 inversion lines with those from five optically thin rotational transitions of HC 3 N, observed at similar frequencies, constrains potential variations of the proton-to-electron mass ratio μ to Δμ/μ < 1.4 × 10 −6 with 3-σ confidence. Also including optically thin rotational lines from other molecular species, it is emphasized that systematic errors are ΔV < 1 km s −1 , corresponding to Δμ/μ < 1.0 × 10 −6 .

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“…The electronvibro-rotational transitions have different dependences on the reduced mass and can be used to constrain the variability of μ (Thompson 1975;Varshalovich & Levshakov 1993). The measurements of μ rely on the same H 2 systems observed with VLT/UVES and claim a variability of Δμ/μ = 24 ± 6 ppm (Reinhold et al 2006) or no variability with −15 ppm < Δμ/μ < 57 ppm (Levshakov et al 2002), |Δμ/μ| ≤ 49 ppm (Wendt & Reimers 2008), Δμ/μ = 2.6 ± 3.0 ppm (King et al 2008), and Δμ/μ = −7 ± 8 ppm (Thompson et al 2009). Radio astronomical observations place constraints on μ-variations of |Δμ/μ| < 1.8 ppm at redshift z = 0.68 (Murphy et al 2008b), and |Δμ/μ| < 0.6 ppm at z = 0.89 (Henkel et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Searching for chameleon-like scalar fields with the ammonia method

Levshakov

Molaro

Lapinov

et al. 2010

A&A

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Aims. We probe the dependence of the electron-to-proton mass ratio, μ = m e /m p , on the ambient matter density by means of radio astronomical observations. Methods. The ammonia method, which has been proposed to explore the electron-to-proton mass ratio, is applied to nearby dark clouds in the Milky Way. This ratio, which is measured in different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter is supposed to vary in chameleon-like scalar field models, which predict strong dependences of both masses and coupling constant on the local matter density. High resolution spectral observations of molecular cores in lines of NH 3 (J, K) = (1, 1), HC 3 N J = 2−1, and N 2 H + J = 1−0 were performed at three radio telescopes to measure the radial velocity offsets, ΔV ≡ V rot − V inv , between the inversion transition of NH 3 (1,1) and the rotational transitions of other molecules with different sensitivities to the parameter Δμ/μ ≡ (μ obs − μ lab )/μ lab . Results. The measured values of ΔV exhibit a statistically significant velocity offset of 23 ± 4 stat ± 3 sys m s −1 . When interpreted in terms of the electron-to-proton mass ratio variation, this infers that Δμ/μ = (2.2 ± 0.4 stat ± 0.3 sys ) × 10 −8 . If only a conservative upper bound is considered, then the maximum offset between ammonia and the other molecules is |ΔV| ≤ 30 m s −1 . This provides the most accurate reference point at z = 0 for Δμ/μ of |Δμ/μ| ≤ 3 × 10 −8 .

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Indication of a Cosmological Variation of the Proton-Electron Mass Ratio Based on Laboratory Measurement and Reanalysis ofH2Spectra

Cited by 285 publications

References 21 publications

Testing the time-invariance of fundamental constants using microwave spectroscopy on cold diatomic radicals

Testing the time-invariance of fundamental constants using microwave spectroscopy on cold diatomic radicals

The density, the cosmic microwave background, and the proton-to-electron mass ratio in a cloud at redshift 0.9

Searching for chameleon-like scalar fields with the ammonia method

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