EGAS41 - Swansea University

41 st EGAS CP 118 Gdańsk 2009
Precision spectroscopy of the 3s-3p fine-structure doublet
in Mg +
V. Batteiger 1,∗ , M. Herrmann 1 , S. Knünz 1 , G. Saathoff 1 , T. Udem 1 , T.W. Hänsch 1
1 Max-Planck-Institute of Quantum Optics, Hans-Kopfermann-Str. 1, D-85748 Garching,
Germany
∗ Corresponding author: valentin.batteiger@mpq.mpg.de,
Precision spectroscopy on single trapped ions has reached tremendous accuracies by probing
narrow transitions in the resolved-sideband regime [1]. However, a variety of interesting
transitions may not be studied in this regime, because their transition linewidths
well exceed common (secular) trap frequencies. Accurate spectroscopy is then challenging,
since an interrogating laser induces detuning-dependent heating and cooling which
distorts the line profile. We present both theory and experimental demonstration of a
spectroscopic method (Fig.1) which overcomes these limitations and allows to observe
essentially unperturbed Voigt profiles with high signal-to-noise ratio (Fig.2) [2].
Figure 1: An ion chain is continuously laser cooled at one side only, a weak spectroscopy
laser along the trap axis probes sympathetically cooled ions. This method allows for efficient
sympathetic cooling, minimizes light shifts and background photons.
3000
2500
2000
Counts/3s
1500
1000
500
0
180 200 220 240 260 280 300 320 340 360 380 400
Optical Frequency - 1 072 082 630 [MHz]
Figure 2: Typical line scan from a single trapped 24 Mg + ion.
We deduce absolute frequency reference data for transition frequencies, isotope shifts
and fine structure splittings that are in particular useful for comparison with quasar absorption
spectra, to test possible space-time variations of the fine structure constant [3,4].
The measurement accuracy improves previous literature values, when existing, by more
than two orders of magnitude.
References
[1] T. Rosenband et al., Science 319, 1808 (2008)
[2] M. Herrmann et al., Phys. Rev. Lett. 102, 013006 (2009)
[3] J.K. Webb et al., Phys. Rev. Lett. 82, 884, (1999)
[4] J.C. Berengut et al., arXiv:physics/0408017, (2006)
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