g-factor measurement of hydrogenlike ²⁸Si¹³⁺ as a challenge to QED calculations

S. Sturm, A. Wagner, M. Kretzschmar, W. Quint, G. Werth, and K. Blaum

Accepted Tuesday Jan 29, 2013

Using a phase-detection method to determine the cyclotron frequency of a single trapped ion in a Penning trap allowed us to perform an improved measurement of the g-factor of the bound electron in hydrogenlike 28Si13+ with a statistical uncertainty of 4·10-11. Furthermore, we reevaluated the image-charge shift as the main source of uncertainty. Our result challenges bound-state quantum-electrodynamical calculations by probing for the first time two-loop contributions of order (Za)6 and paves the way towards a more precise determination of fundamental constants as the electron mass.