High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED

Abstract

Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209Bi82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron–nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209Bi82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction.

QED tests with highly charged ions

“…It was thus shown in [460], that the integrals over the atomic wavefunction for the 1s and 2s, which are used to evaluate the Bohr-Weisskopf correction (see, e.g., equations (4) to (8) in [465]) differ only by an overall factor, leading to (40). Using the new magnetic moment and theoretical values obtained in [421] and the corresponding HFS energy, one obtains ∆E HFS = 0.061 043(5) eV (30), while the theoretical value from Volotka et al [440], rescaled with the new magnetic moment value is −0.061 042(64) eV and the experimental value 0.061 012(5) (21) [450]. All three values are thus in excellent agreement.…”

“…. So while the new calculations and measurements of the 209 Bi magnetic moments [421,422] enabled to solve the hyperfine structure puzzle found in the experiment [450], it does not improve our capacity to test QED. New experiments are planed to work on this aspect, like a measurement of the hyperfine structure of 208 Bi at the ESR to be able to have system with identical atomic properties and different nuclear corrections.…”

A novel ppm-precise absolute calibration method for precision high-voltage dividers

“…Precision measurements of direct current (DC) high voltage (HV) are important for many applications in physics, e.g. to record an integral spectrum of tritium-β-electrons with the KATRIN neutrino mass experiment [1] or for determining kinetic energies of electrons with electron coolers at ion storage rings [2]. The scope of applications is not limited to fundamental research, but is also important for high-voltage direct current (HVDC) electric power transmission systems, which are currently discussed and planned as part of the "energy transition" in many European countries.…”

Studies at the border between nuclear and atomic physics: Weak decays of highly charged ions

“…The electrons are efficiently stripped away from energetic particles while passing through target material [21][22][23]. Fully-ionised and up to 4-electron ions are routinely produced at energies of about 100 − 400 A MeV [24][25][26][27][28][29][30][31][32][33][34][35]. The selection of the atomic charge state is done by optimising the primary projectile energy, target material and its thickness [36].…”