We present the measurements of individual bound electron g factors of 20Ne9+ and 22Ne9+ on the relative level of 0.1 parts per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in m(20Ne)=19.99244016877(9)u, which improves the current literature value by a factor of 18, disagrees by 4 standard deviations, and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of 0.1 ppb with me=5.48579909099(59)×104u as well as a factor of seven improved m(22Ne)=21.9913850982(26)u.

F. Heiße, M. Door, T. Sailer, P. Filianin, J. Herkenhoff, C. M. König, K. Kromer, D. Lange,
J. Morgner, A. Rischka, Ch. Schweiger, B. Tu, Y. N. Novikov, S. Eliseev, S. Sturm, K. Blaum, „High-Precision Determination of g Factors and Masses of 20Ne9+ and 22Ne9+“, Phys. Rev.Lett. 131, 253002 (2023).


Related to Project B01