The nuclear magnetic moment of 208Bi and its relevance for a test of bound-state strong-field QED

S Schmidt,J Billowes,M.L Bissell,K Blaum,R.F Garcia Ruiz,H Heylen,S Malbrunot-Ettenauer,G Neyens,W Nörtershäuser,G Plunien,S Sailer,V.M Shabaev,L.V Skripnikov,I.I Tupitsyn,A.V Volotka,X.F Yang

doi:10.1016/j.physletb.2018.02.024

Abstract

The hyperfine structure splitting in the 6p3S3/24→6p27sP1/24 transition at 307 nm in atomic 208Bi was measured with collinear laser spectroscopy at ISOLDE, CERN. The hyperfine A and B factors of both states were determined with an order of magnitude improved accuracy. Based on these measurements, theoretical input for the hyperfine structure anomaly, and results from hyperfine measurements on hydrogen-like and lithium-like 209Bi80+,82+, the nuclear magnetic moment of 208Bi has been determined to μ(Bi208)=+4.570(10)μN. Using this value, the transition energy of the ground-state hyperfine splitting in hydrogen-like and lithium-like 208Bi80+,82+ and their specific difference of −67.491(5)(148) meV are predicted. This provides a means for an experimental confirmation of the cancellation of nuclear structure effects in the specific difference in order to exclude such contributions as the cause of the hyperfine puzzle, the recently reported 7-σ discrepancy between experiment and bound-state strong-field QED calculations of the specific difference in the hyperfine structure splitting of 209Bi80+,82+.

Highlights

Since its development in 1947, the theory of quantum electrodynamics (BS-QED), a major keystone within the standard model of physics, has an impressive and long history of success [1,2,3,4] and has so far mastered all tests in light systems [5,6] with unprecedented accuracy
Besides the measurements of the Lamb-shift [10,11,12] and the Landé g-factor [13,14,15,16] in highly charged ions (HCIs), one promising quantity to access this non-perturbative regime of BS-QED is the ground-state hyperfine structure splitting in hydrogen-like (H-like) ions, nowadays accessible by high-precision laser spectroscopy
The voltage applied to the radiofrequency quadrupole (RFQ) defines the starting potential of the ion bunch for collinear laser spectroscopy

Summary

Introduction

Since its development in 1947, the theory of (bound-state) quantum electrodynamics (BS-QED), a major keystone within the standard model of physics, has an impressive and long history of success [1,2,3,4] and has so far mastered all tests in light systems [5,6] with unprecedented accuracy. Previous direct tests of BS-QED via the transition energy of various ground-state hfs splittings in H-like ions [17,18,19] could not be exploited due to the large uncertainty in the theoretical predictions, mainly arising from the magnetic moment distribution over the finite nuclear size, the Bohr-Weisskopf effect [20].

Methods

Results

Conclusion