The 435 /spl mu/m /sup 171/Yb/sup +/ transition is a good candidate for an atomic clock based on an optical transition. We have stored single /sup 171/Yb ions for several months in RF traps. The ions are cooled, repumped and the clock transition is interrogated by (frequency-doubled) diode lasers. The interrogation laser linewidth was 30 Hz determining the resolvable linewidth of the Yb/sup +/ transition interrogated. The absolute frequency of this transition was measured using an optical comb generator, self referenced by broadening the spectrum to above one octave, with respect to a Cs fountain clock. Of all systematic frequency shifts to which this transition is subject an estimate indicates that the electric quadruple shift appears is the largest. To obtain a magnitude of the quadruple shift (and the quadruple moment) the clock frequencies of two independently stored and cooled /sup 171/Yb ions were compared while varying the static electric field in one trap. The measured frequency shift amounting to /spl sim/1 Hz/V. This result would seem to permit clocks with much higher accuracy than the clocks based on microwave transition, particularly if the technique of aligning the ions with respect to the electric field were applicable. Anticipating even more precise clocks, we are presently investigating a blue nuclear transition in /sup 229/Th. Such a nuclear transition should be even better shielded from environmental influences than transitions in the electron shell. This nuclear transition has not yet been directly optically observed. We are presently investigating the luminescence after incoherent broad band optical excitation. The triply ionized /sup 223/Th is then a suitable system for trapped single ion spectroscopy. The cooling transition lies conveniently in the near infrared and the nuclear clock transition can be read out by nuclear/electron shell double resonance.
Single ion spectroscopy for optical clocks
2003-01-01
65481 byte
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
Single Ion Spectroscopy for Optical Clocks
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