Phys. Rev. Lett. 100, 150801 (2008) [4 pages]Stability of the Proton-to-Electron Mass RatioReceived 7 December 2007; published 18 April 2008 We report a limit on the fractional temporal variation of the proton-to-electron mass ratio as 1/(mP/me)∂/∂t(mP/me)=(-3.8±5.6)×10-14 yr-1, obtained by comparing the frequency of a rovibrational transition in SF6 with the fundamental hyperfine transition in Cs. The SF6 transition was accessed using a CO2 laser to interrogate spatial 2-photon Ramsey fringes. The atomic transition was accessed using a primary standard controlled with a Cs fountain. This result is direct and model-free. © 2008 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.100.150801
DOI:
10.1103/PhysRevLett.100.150801
PACS:
06.20.Jr, 06.30.Ft, 33.20.Ea, 42.62.Eh
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