Speaker
Description
Quantum electrodynamics (QED) is one of the most successful fundamental theories to date. With
the g-2 measurement of the free electron, QED interaction has been tested rigorously [1]. Using a
highly charged ion (HCI), one can similarly test bound-state QED effects. This allows to test the
interaction of the electron with the strong electric field present in the vicinity of the nucleus. So far
the regime of the heaviest ions has been explored exclusively via Lamb shift measurements of 1s-
and 2s-shell electrons [2, 3]. Similar the bound-electron g factor can be measured and compared to
theory to perform tests of QED in heavy HCI [4, 5]. Until now, g-factor measurements were limited
to low-Z ions, as the production of heavy HCI requires large experimental setups.
Here we present a QED test using a hydrogenlike 118Sn49+ ion. From an external electron beam ion
trap (HD-EBIT) [6], we inject the HCIs into our Penning-trap setup [7]. A single ion is isolated, and
its bound-electron g factor is measured with a relative precision of 4.6×10−9, limited solely by the
mass uncertainty of the 118Sn isotope. The comparison with our ab-initio theory calculation allows a
stringent test, matching the stringency of the previous Lamb-shift measurements.
This result marks a key step for g-factor QED tests into the high-Z region. Furthermore, our experi-
mental result surpasses the current theory precision by far and thus establishes the basis for order of
magnitude improved sensitivity, once currently ongoing theory calculations succeed.
[1] D. Hanneke, S. Fogwell, G. Gabrielse, Phys. Rev. Lett. 100, 120801 (2008)
[2] P. Beiersdorfer, et al. Phys. Rev. Lett. 95, 233003 (2005)
[3] A. Gumberidze, et al. Phys. Rev. Lett. 94, 341001 (2005)
[4] T. Beier, Physics Reports 339, 79–213 (2000)
[5] S. Sturm et al., Phys. Rev Lett. 107, 023002 (2011)
[6] A. J. G. Martínez et al., Journal of Physics: Conference Series 72, 012001 (2007)
[7] S. Sturm et al., The European Physical Journal Special Topics 227, 1425–1491 (2019)
