News Archive (2008 - 2023)

Quantum electrodynamics (QED) is part of the Standard Model of particle physics, which has the ambitious goal of describing all physical effects with the exception of gravity. Tests of the Standard Model are of interest to find clues as to why some predictions do not match experimental observations.
The strength of the magnetic moment of a single electron bound to the nucleus of an atom is determined by the so-called g-factor. The comparison of the experimental g-factor and the g-factor calculated from QED models allows to test current QED models with very high accuracy.

In a recent article published in "Physical Review Letters" members of our division report on the measurements of individual bound electron g-factors of ²⁰Ne⁹⁺ and ²²Ne⁹⁺. The g-factor experiments were performed using the cryogenic Penning-trap setups ALPHATRAP and PENTATRAP at MPIK Heidelberg. In order to determine the g-factor, the nuclear mass of neon and the Larmor frequency (precession frequency of the spin of the stored neon ion in the magnetic field) are required. The Larmor frequency was determined in the ALPHATRAP experiment. The nuclear mass of ²⁰Ne was determined by the PENTATRAP experiment with a precision of 5·10^–12. This is a world record for mass measurements in atomic mass units. Using the nuclear mass and the Larmor frequency, the g-factor of the bound electron in ²⁰Ne⁹⁺ and ²²Ne⁹⁺ was determined with a relative precision of 10^–10.
The comparison of the experimental g-factor and the g-factor calculated from QED models shows an agreement to ten decimal places and provides the most precise test of the theory of self-interaction of the bound electron.

Please read more in the article ... >

Further information also in the press release of the MPIK 

Modern atomic clocks are among the most accurate measurement tools. They are the basis of advanced technology like the GPS system. The invention of the frequency comb opened the path to atomic clocks using optical transitions in trapped, single, highly charged ions (HCI).
In a recent article published in "Physical Review Letters" members of our division report on the identification of a metastable electronic state in highly charged lead ions (Nb-like ²⁰⁸Pb⁴¹⁺) which could be used as a clock state. The Penning-trap mass spectrometer PENTATRAP was used to directly determine the excitation energy of the metastable state in Pb⁴¹⁺ ions to be 31.2(8) eV. With a fractional mass uncertainty of 4·10^–12 this is one of the most precise mass measurements to date.
The experimental work was combined with a theoretical work from the division of Christoph Keitel at MPIK and Paul Indelicato from the Sorbonne University, in which the transition energy was theoretically determined with two extensive, partially different ab initio multi-configuration Dirac-Hartree-Fock calculations.

Please read more in the article ... >

Further information also in the press release of the MPIK 

The Cabibbo-Kobayashi-Maskawa (CKM) matrix is a central cornerstone in the formulation of the Standard Model of particle physics. For the Standard Model to be complete, the CKM matrix must be unitary. The first element in the top row of the matrix, V_ud, can be extracted from measurements of beta-decay rates, considering theoretical corrections such as the nuclear charge distribution (nuclear charge radius).
In ^26mAl, those corrections are very small and it has one of the most precisely measured beta-decay rates that constrains the V_ud value. Thus, ^26mAl is of particular importance for the determination of V_ud.

In a recent article published in "Physical Review Letters", P. Plattner et al. report on the first experimental determination of the nuclear charge radius of ^26mAl by collinear laser spectroscopy. For this purpose, two independent experiments were performed. One at the COLLAPS beamline at ISOLDE-CERN and the other at the IGISOL CLS beamline in Jyväskylä, Finland. The new precise charge radius value R_c=3.130(15) fm of ^26mAl directly affects the determination of V_ud and thus the testing of CKM-matrix unitarity.

Please read more in the article ... >

Further information also in the press release of CERN 

The article has been selected for a Viewpoint in Physics. Please read also the viewpoint on the article  by T. E. Cocolios (KU Leuven).

The article has also been selected as "Editor's Suggestion". This is an award "based on the potential interest in the results presented and, importantly, on the success of the paper in communicating its message, in particular to readers from other fields" (see also here )