A search for varying fundamental constants using hertz-level frequency measurements of cold CH molecules.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 24129439.
- Also identified by DOI 10.1038/ncomms3600 and PMC identifier 3826645.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Many modern theories predict that the fundamental constants depend on time, position or the local density of matter. Here we develop a spectroscopic method for pulsed beams of cold molecules, and use it to measure the frequencies of microwave transitions in CH with accuracy down to 3 Hz. By comparing these frequencies with those measured from sources of CH in the Milky Way, we test the hypothesis that fundamental constants may differ between the high- and low-density environments of the Earth and the interstellar medium. For the fine structure constant we find Δα/α=(0.3 ± 1.1) × 10⁻⁷, the strongest limit to date on such a variation of α. For the electron-to-proton mass ratio we find Δμ/μ=(-0.7 ± 2.2) × 10⁻⁷. We suggest how dedicated astrophysical measurements can improve these constraints further and can also constrain temporal variation of the constants.