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Volume 142, 2009
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Testing the time-invariance of fundamental constants using microwave spectroscopy on cold diatomic radicals

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Abstract

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 = 6, Ω = 1 and the J = 8, Ω = 0 levels of the various natural isotopomers of carbon monoxide in its a3Π state. As a result, the 2-photon transition that connects these states is 300 times more sensitive to a variation of mp/me than a pure rotational transition. We present a molecular beam apparatus that might be used to measure these transitions with a fractional accuracy of 10−12. Ultimately, the precision of an experiment on metastable CO will be limited by the lifetime of the a3Π 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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Publication details

The article was received on 28 Oct 2008, accepted on 05 Jan 2009 and first published on 27 May 2009


Article type: Paper
DOI: 10.1039/B819099B
Citation: Faraday Discuss., 2009,142, 25-36
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    Testing the time-invariance of fundamental constants using microwave spectroscopy on cold diatomic radicals

    H. L. Bethlem and W. Ubachs, Faraday Discuss., 2009, 142, 25
    DOI: 10.1039/B819099B

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