Progress at NIST toward absolute frequency standards using stored ions

Abstract

Experiments directed toward the realization of frequency standards of high accuracy using stored ions are briefly summarized. In one experiment, an RF oscillator is locked to a nuclear spin-flip hyperfine transition (frequency approximately= 3.03*10/sup 8/ Hz) in /sup 9/Be/sup +/ ions that are stored in a Penning trap and sympathetically laser-cooled. Stability is better than 3*10/sup -12/ tau /sup -(1/2)/ and uncertainty in Doppler shifts is estimated to be less than 5*10/sup -15/. In a second experiment, a stable laser is used to probe an electric quadrupole transition (frequency approximately=1.07*10/sup 15/ Hz) in a single laser-cooled /sup 199/Hg/sup +/ ion stored in a Paul trap. The measured Q value of this transition is approximately 10/sup 13/. Future possible experiments are discussed.<>