Radio-frequency E1 transitions between nearly degenerate, opposite parity levels of atomic dysprosium were monitored over an eight month period to search for a variation in the fine-structure constant. During this time period, data were taken at different points in the gravitational potential of the Sun. The data are fitted to the variation in the gravitational potential yielding a value of (−8.7 ± 6.6) × 10 −6 for the fit parameter kα. This value gives the current best laboratory limit. In addition, our value of kα combined with other experimental constraints is used to extract the first limits on ke and kq. These coefficients characterize the variation of me/mp and mq/mp in a changing gravitational potential, where me, mp, and mq are electron, proton, and quark masses. The results are ke = (4.9 ± 3.9) × 10 −5 and kq = (6.6 ± 5.2) × 10 −5 .Similarly, the change of the rf transition frequency between levels A and B, as shown in Fig. 1, is given by
Radio-frequency electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored over an eight-month period to search for a variation in the fine-structure constant, α. The data provide a rate of fractional temporal variation of α of (−2.4±2.3)×10 −15 yr −1 or a value of (−7.8 ± 5.9) × 10 −6 for kα, the variation coefficient for α in a changing gravitational potential. All results indicate the absence of significant variation at the present level of sensitivity. We also present initial results on laser cooling of an atomic beam of dysprosium.
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