Laser spectroscopy measurement of the 2s-hyperfine splitting in lithium-like bismuth

Abstract

We have recently reported on the first direct measurement of the 2s hyperfine transition in lithium-like bismuth 209 Bi 80+. Combined with a new measurement of the 1s hyperfine splitting in the hydrogen-like 209 Bi 82+ the so-called specific difference ∆ E = −61.37(36) meV was determined and is in good agreement with the strong-field bound-state QED prediction. Here we report on additional investigations performed to estimate systematic uncertainties of these results and on details of the experimental setup. We show that the dominating uncertainty arises from the insufficient knowledge of the ion beam velocity determined from the electroncooler voltage. Two routes to obtain a cooler-voltage calibration are discussed and it is shown that agreement in ∆ E with the QED calculations and of the hyperfine splitting in hydrogen-like bismuth as reported in the first measurement in 1994 are mutually exclusive.

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

“…A measurement of the electron cooler voltage thus provides the required information on β for the Doppler transformation into the ions' rest frame. In our case the cooler voltage was ≈214 kV and a reliable measurement of such a high voltage was not available during the previous beamtime, leading to the dominant systematic uncertainty reported in refs 13, 32. Here, this issue was resolved by an in-situ measurement using an accurate high-voltage divider built at PTB Braunschweig, the German National Metrology Institute33.…”

Lifetimes and g-factors of the HFS states in H-like and Li-like bismuth

“…The main part of the LIBELLE beam-time in 2014 was spent on the precise determination of the wavelengths of the HFS transitions in 209 Bi 82+ and 209 Bi 80+ . For that purpose the laser wavelength was scanned repeatedly across the respective transitions and a number of dedicated systematics measurements, among others investigating the influence of the electron cooler current or the buncher amplitude on the observed transition wavelength, were performed [4,5]. In addition to this, some runs were recorded in which the laser was fixed to the transition wavelength of either 209 Bi 82+ or 209 Bi 80+ (in the latter case with the optical shutter system in operation) to obtain high statistics data on the lifetime of the states.…”

Electroweak Decays of Highly Charged Ions

“…Fully-ionised and up to 4-electron ions are routinely produced at energies of about 100 − 400 MeV/u, see, e.g., Refs. [43][44][45][46][47][48][49][50][51][52][53][54].…”

“…Since typical weak lifetimes are longer than about a ms, for their investigations one requires facilities which are capable to store the produced radionuclides in a preserved high charged state for a sufficiently long time. Apart from the recent studies in the Electron Beam Ion Trap (EBIT) at TRIUMF [23,24], very recent measurements of weak decays of fullyionized 49 Cr 24+ , 53 Fe 26+ atoms [25] and the de-excitation of the 94m Ru 44+ isomeric state [26] at the experimental cooler storage ring CSRe at Institute for Modern Physics (IMP), Lanzhou, all other investigations of decays of HCRs were performed in the ESR of GSI [2][3][4]27].…”