2005/04/14 by E. Peik, B. Lipphardt, H. Schnatz +3
Physics and Astronomy · #physics.atom-ph
published as Laser Physics 15, 1028 (2005) · 12 pages, 5 figures, Proceedings of MPLP'04, Novosibirsk, August 22.-27., 2004
arxiv created 2005/04/14 · arxiv updated 2009/12/01
We describe experiments with an optical frequency standard based on a laser cooled 171Yb+ ion confined in a radiofrequency Paul trap. The electric-quadrupole transition from the 2S1/2(F=0) ground state to the 2D3/2(F=2) state at the wavelength of 436 nm is used as the reference transition. In order to compare two 171Yb+ standards, separate frequency servo systems are employed to stabilize two probe laser frequencies to the reference transition line centers of two independently stored ions. The experimental results indicate a relative instability (Allan standard deviation) of the optical frequency difference between the two systems of σy(1000 \rm s)=5⋅ 10-16 only, so that shifts in the sub-hertz range can be resolved. Shifts of several hertz are observed if a stationary electric field gradient is superimposed on the radiofrequency trap field. The absolute optical transition frequency of Yb+ at 688 THz was measured with a cesium atomic clock at two times separated by 2.8 years. A temporal variation of this frequency can be excluded within a 1σ relative uncertainty of 4.4⋅ 10-15 yr-1. Combined with recently published values for the constancy of other transition frequencies this measurement provides a limit on the present variability of the fine structure constant α at the level of 2.0⋅ 10-15 yr-1.