Frequency Measurement of the Electric Quadrupole Transition in a Single Laser-Cooled 40 Ca +

This is the authors' abstract. We don't add key points for this paper.

The optical frequency of the 4s 2 S 1/2 -3d 2 D 5/2 transition in a single trapped and laser-cooled 40 Ca + ion is measured with an optical frequency comb system referenced to a hydrogen maser. A 729-nm laser can be locked to the clock transition about ten hours and the Allan deviation is better than 2 × 10 −14 /1000 s.