0000000000347608
AUTHOR
Sven Sturm
High-precision measurement of the atomic mass of the electron
A very precise measurement of the magnetic moment of a single electron bound to a carbon nucleus, combined with a state-of-the-art calculation in the framework of bound-state quantum electrodynamics, gives a new value of the atomic mass of the electron that is more precise than the currently accepted one by a factor of 13. The atomic mass of the electron is a key parameter for fundamental physics. A precise determination is a challenge because the mass is so low. Sven Sturm and colleagues report on a new determination of the electron's mass in atomic units. The authors measured the magnetic moment of a single electron bound to a reference ion (a bare nucleus of carbon-12). The results were …
Theg-factor of highly charged ions
Highly charged ions provide a unique opportunity to test our understanding of atomic properties under extreme conditions: The electric field strength seen by an electron bound to a nucleus at the distance of the Bohr radius ranges from 1010 V/cm in hydrogen to1016 V/cm in hydrogenlike uranium. The theory of quantum electrodynamics (QED) allows for calculation e.g. of binding energies, transition probabilities or magnetic moments. While at low fields QED is tested to very high precision, new, hypothetical nonlinear effects like photon- photon interaction or a violation of Lorentz symmetry may occur in strong fields which then would lead to an extension of the Standard Model. The ultra-high p…
A battery-based, low-noise voltage source.
A highly stable, low-noise voltage source was designed to improve the stability of the electrode bias voltages of a Penning trap. To avoid excess noise and ground loops, the voltage source is completely independent of the public electric network and uses a 12 V car battery to generate output voltages of +/-15 and +/-5 V. First, the dc supply voltage is converted into ac-voltage and gets amplified. Afterwards, the signal is rectified, filtered, and regulated to the desired output value. Each channel can deliver up to 1.5 A. The current as well as the battery voltage and the output voltages can be read out via a universal serial bus (USB) connection for monitoring purposes. With the presented…
Investigation of Space-Charge Phenomena in Gas-Filled Penning Traps
The centering of ions in Penning traps by a quadrupolar radiofrequency excitation in the presence of a buffer gas has been studied in the regime of high charge‐densities. It is found to deviate significantly from the single‐particle situation. In particular, the efficiency of the cooling process is affected as well as the resolving power. The behavior has been studied experimentally at the preparation trap REXTRAP and the high‐precision Penning trap setup ISOLTRAP both located at the on‐line mass separator ISOLDE at CERN. In addition, the phenomenon has been investigated numerically by a custom‐designed simulation.
g Factor of Lithiumlike Silicon: New Challenge to Bound-State QED
The recently established agreement between experiment and theory for the $g$ factors of lithiumlike silicon and calcium ions manifests the most stringent test of the many-electron bound-state quantum electrodynamics (QED) effects in the presence of a magnetic field. In this Letter, we present a significant simultaneous improvement of both theoretical $g_\text{th} = 2.000\,889\,894\,4\,(34)$ and experimental $g_\text{exp} = 2.000\,889\,888\,45\,(14)$ values of the $g$ factor of lithiumlike silicon $^{28}$Si$^{11+}$. The theoretical precision now is limited by the many-electron two-loop contributions of the bound-state QED. The experimental value is accurate enough to test these contributions…
g-factor measurement of hydrogenlike28Si13+as a challenge to QED calculations
Using a phase-detection method to determine the cyclotron frequency of a single trapped ion in a Penning trap allowed us to perform a measurement of the $g$ factor of the bound electron in hydrogenlike ${}^{28}$Si${}^{13+}$ with a statistical uncertainty of $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$. Furthermore, we reevaluated the image-charge shift as the main source of uncertainty. Our result challenges bound-state quantum-electrodynamical calculations by probing two-loop contributions of order (Z$\ensuremath{\alpha}$)${}^{6}$ and paves the way towards a more precise determination of fundamental constants as the electron mass.
Electrong-factor determinations in Penning traps
The magnetic moment of the electron, expressed by the g-factor in units of the Bohr magneton, is a key quantity in the theory of quantum electrodynamics (QED). Experiments using single particles confined in Penning traps have provided very precise values of the g-factor for the free electron as well as the electron bound in hydrogen-like ions. In this paper the status of these experiments is reviewed. The results allow testing calculations of higher order Feynman diagrams. Comparison of experimental and theoretical results for free and bound particles show no discrepancy within the limits of error, thus representing to date the most sensitive test of QED. Moreover, the g-factor provides a u…
High-Precision Measurements of the Bound Electron’s Magnetic Moment
Highly charged ions represent environments that allow to study precisely one or more bound electrons subjected to unsurpassed electromagnetic fields. Under such conditions, the magnetic moment (g-factor) of a bound electron changes significantly, to a large extent due to contributions from quantum electrodynamics. We present three Penning-trap experiments, which allow to measure magnetic moments with ppb precision and better, serving as stringent tests of corresponding calculations, and also yielding access to fundamental quantities like the fine structure constant α and the atomic mass of the electron. Additionally, the bound electrons can be used as sensitive probes for properties of the …
Isotope dependence of the Zeeman effect in lithium-like calcium
The magnetic moment μ of a bound electron, generally expressed by the g-factor μ=−g μB s ħ−1 with μB the Bohr magneton and s the electron's spin, can be calculated by bound-state quantum electrodynamics (BS-QED) to very high precision. The recent ultra-precise experiment on hydrogen-like silicon determined this value to eleven significant digits, and thus allowed to rigorously probe the validity of BS-QED. Yet, the investigation of one of the most interesting contribution to the g-factor, the relativistic interaction between electron and nucleus, is limited by our knowledge of BS-QED effects. By comparing the g-factors of two isotopes, it is possible to cancel most of these contributions an…
High-precision measurement of the proton's atomic mass
We report on the precise measurement of the atomic mass of a single proton with a purpose-built Penning-trap system. With a precision of 32 parts-per-trillion our result not only improves on the current CODATA literature value by a factor of three, but also disagrees with it at a level of about 3 standard deviations.
Image charge shift in high-precision Penning traps
An ion in a Penning trap induces image charges on the surfaces of the trap electrodes. These induced image charges are used to detect the ion's motional frequencies, but they also create an additional electric field, which shifts the free-space cyclotron frequency typically at a relative level of several ${10}^{\ensuremath{-}11}$. In various high-precision Penning-trap experiments, systematics and their uncertainties are dominated by this so-called image charge shift (ICS). The ICS is investigated in this work by a finite-element simulation and by a dedicated measurement technique. Theoretical and experimental results are in excellent agreement. The measurement is using singly stored ions a…
High-precision mass spectrometer for light ions
The precise knowledge of the atomic masses of light atomic nuclei, e.g. the proton, deuteron, triton and helion, is of great importance for several fundamental tests in physics. However, the latest high-precision measurements of these masses carried out at different mass spectrometers indicate an inconsistency of five standard deviations. To determine the masses of the lightest ions with a relative precision of a few parts per trillion and investigate this mass problem a cryogenic multi-Penning trap setup, LIONTRAP (Light ION TRAP), was constructed. This allows an independent and more precise determination of the relevant atomic masses by measuring the cyclotron frequency of single trapped …
gFactor of HydrogenlikeSi13+28
We determined the experimental value of the $g$ factor of the electron bound in hydrogenlike $^{28}\mathrm{Si}^{13+}$ by using a single ion confined in a cylindrical Penning trap. From the ratio of the ion's cyclotron frequency and the induced spin flip frequency, we obtain $g=1.995\text{ }348\text{ }958\text{ }7(5)(3)(8)$. It is in excellent agreement with the state-of-the-art theoretical value of 1.995 348 958 0(17), which includes QED contributions up to the two-loop level of the order of $(Z\ensuremath{\alpha}{)}^{2}$ and $(Z\ensuremath{\alpha}{)}^{4}$ and represents a stringent test of bound-state quantum electrodynamics calculations.
Zeeman Spectroscopy in Penning Traps
Abstract Penning traps are the instruments of choice to determine the magnetic moments of long lived or stable charged particles. The virtual absence of collisions with background molecules when working in ultra-high vacuum, the small volume which the trapped particles occupy at low kinetic energies, and the extremely long observation and coherence times allow for very high precision in Zeeman spectroscopy. When applied to singly ionized multielectron atoms the experiments serve for tests of atomic structure calculations. The magnetic moments in few-electron systems such as hydrogen- or lithium-like highly charged ions can be calculated with remarkable precision in the frame of bound-state …