Hyperfine structure of CH3OH

Heuvel, J.E.M.; Dymanus, A.

doi:10.1016/0022-2852(73)90159-8

Cited by 21 publications

(62 citation statements)

References 6 publications

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“…The RMS error was estimated by cross-correlating 10 4 pairs of simulated spectra, obtained by adding independent representations of Gaussian noise to the best-fit profiles, with the noise spectra char-2 Note that little is known about the CH 3 OH hyperfine structure which has been ignored here. For a few lines, Heuvel & Dymanus (1973) find the hyperfine structure extends over 50 kHz, i.e. smaller than our channel spacing; it should have a negligible effect on our results.…”

Section: Observations Data Analysis and Spectracontrasting

confidence: 55%

Constraints on changes in the proton–electron mass ratio using methanol lines

Kanekar

Ubachs

Menten

et al. 2015

Monthly Notices of the Royal Astronomical Society: Letters

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We report Karl G. Jansky Very Large Array (VLA) absorption spectroscopy in four methanol (CH 3 OH) lines in the z = 0.88582 gravitational lens towards PKS1830−211. Three of the four lines have very different sensitivity coefficients K µ to changes in the proton-electron mass ratio µ; a comparison between the line redshifts thus allows us to test for temporal evolution in µ. We obtain a stringent statistical constraint on changes in µ by comparing the redshifted 12.179 GHz and 60.531 GHz lines, [∆µ/µ] 1.1 × 10 −7 (2σ) over 0 < z 0.88582, a factor of ≈ 2.5 more sensitive than the best earlier results. However, the higher signal-to-noise ratio (by a factor of ≈ 2) of the VLA spectrum in the 12.179 GHz transition also indicates that this line has a different shape from that of the other three CH 3 OH lines (at > 4σ significance). The sensitivity of the above result, and that of all earlier CH 3 OH studies, is thus likely to be limited by unknown systematic errors, probably arising due to the frequency-dependent structure of PKS1830−211. A robust result is obtained by combining the three lines at similar frequencies, 48.372, 48.377 and 60.531 GHz, whose line profiles are found to be in good agreement. This yields the 2σ constraint [∆µ/µ] 4 × 10 −7 , the most stringent current constraint on changes in µ. We thus find no evidence for changes in the proton-electron mass ratio over a lookback time of ≈ 7.5 Gyrs.

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Section: Observations Data Analysis and Spectracontrasting

confidence: 55%

Constraints on changes in the proton–electron mass ratio using methanol lines

Kanekar

Ubachs

Menten

et al. 2015

Monthly Notices of the Royal Astronomical Society: Letters

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“…4.1, where also some assignments for J > 30 are discussed. Heuvel & Dymanus (1973) give 17 513.34127(20) MHz for the unsplit position of the line marked with x. All lines, except those marked "ND" have been detected in astronomical sources.…”

Section: Comparison With Earlier Resultsmentioning

confidence: 99%

“…The highest accuracy measurements available for lines in the radio frequency and centimeter wavelength ranges, where high accuracy is most important, were made by Radford (1972), Heuvel & Dymanus (1973), and Gaines et al (1974), employing beam-maser spectroscopy. Later, Mehrotra et al (1985) and Breckenridge & Kukolich (1995) employed microwave Fourier transform (MWFT) spectroscopy.…”

Section: Existing Data and New Laboratory Measurementsmentioning

confidence: 99%

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Accurate rest frequencies of methanol maser and dark cloud lines

Müller¹,

Menten

Mäder

2004

A&A

105

100

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Abstract.We report accurate laboratory measurements of selected methanol transition frequencies between 0.834 and 230 GHz in order to facilitate astronomical velocity analyses. New data have been obtained between 10 and 27 GHz and between 60 and 119 GHz. Emphasis has been put on known or potential interstellar maser lines as well as on transitions suitable for the investigation of cold dark clouds. Because of the narrow line widths (<0.5 km s −1 ) of maser lines and lines detected in dark molecular clouds, accurate frequencies are needed for comparison of the velocities of different methanol lines with each other as well as with lines from other species. In particular, frequencies for a comprehensive set of transitions are given which, because of their low energy levels (<20 cm −1 or 30 K), are potentially detectable in cold clouds. Global Hamiltonian fits generally do not yet yield the required accuracy. Additionally, we report transition frequencies for other lines that may be used to test and to improve existing Hamiltonian models.

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“…PRL 111, 231101 (2013) P H Y S I C A L R E V I E W L E T T E R S week ending 6 DECEMBER 2013 Table I contains results from the fitted spectra of all methanol lines observed, as well as laboratory frequencies [15][16][17][18][19] with their uncertainties, and the calculated K coefficients [9]. The quoted optical depths are related to the measured absorption line intensities I via ¼ À lnð1 À I =f c I bg Þ, where I bg is the total continuum intensity and f c is the continuum source covering factor.…”

Section: Transition Lower-uppermentioning

confidence: 99%

Robust Constraint on a Drifting Proton-to-Electron Mass Ratio atz=0.89from Methanol Observation at Three Radio Telescopes

et al. 2013

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A limit on a possible cosmological variation of the proton-to-electron mass ratio μ is derived from methanol (CH3OH) absorption lines in the benchmark PKS1830-211 lensing galaxy at redshift z=0.89 observed with the Effelsberg 100-m radio telescope, the Institute de Radio Astronomie Millimétrique 30-m telescope, and the Atacama Large Millimeter/submillimeter Array. Ten different absorption lines of CH3OH covering a wide range of sensitivity coefficients K(μ) are used to derive a purely statistical 1σ constraint of Δμ/μ=(1.5±1.5)×10(-7) for a lookback time of 7.5 billion years. Systematic effects of chemical segregation, excitation temperature, frequency dependence, and time variability of the background source are quantified. A multidimensional linear regression analysis leads to a robust constraint of Δμ/μ=(-1.0±0.8(stat)±1.0(sys))×10(-7).

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Hyperfine structure of CH3OH

Cited by 21 publications

References 6 publications

Constraints on changes in the proton–electron mass ratio using methanol lines

Constraints on changes in the proton–electron mass ratio using methanol lines

Accurate rest frequencies of methanol maser and dark cloud lines

Robust Constraint on a Drifting Proton-to-Electron Mass Ratio atz=0.89from Methanol Observation at Three Radio Telescopes

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