Measurement of the lowest millimetre-wave transition frequency of the CH radical

Abstract

The CH radical offers a sensitive way to test the hypothesis that fundamental constants measured on earth may differ from those observed in other parts of the universe. The starting point for such a comparison is to have accurate laboratory frequencies. Here we measure the frequency of the lowest millimetre-wave transition of CH, near 535 GHz, with an accuracy of 0.6 kHz. This improves the uncertainty by roughly two orders of magnitude over previous determinations and opens the way for sensitive new tests of varying constants.

5 pages, 5 figures

References in corpus (2)

• Herschel observations of extra-ordinary sources: Detecting spiral arm clouds by CH absorption lines
• Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star-forming core NGC6334I

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• The MPIfR-MeerKAT Galactic Plane survey I -- System setup and early results
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• The CH radical at radio wavelengths: Revisiting emission in the 3.3GHz ground state lines
• Microwave spectroscopy of Lambda-doublet transitions in the ground state of CH
• Cosmo-tomography toward PKS1830-211: Variability of the quasar and of its foreground molecular absorption monitored with ALMA
• Revisiting rotationally excited CH at radio wavelengths: A case study towards W51
• First detection of deuterated methylidyne (CD) in the interstellar medium
• A sub-ppm upper limit on the cosmological variations of the fine structure constant alpha