Measuring the stability of fundamental constants with a network of clocks

The detection of variations of fundamental constants of the Standard Model would provide us with compelling evidence of new physics, and could lift the veil on the nature of dark matter and dark energy. In this work, we discuss how a network of atomic and molecular clocks can be used to look for such variations with unprecedented sensitivity over a wide range of time scales. This is precisely the goal of the recently launched QSNET project: A network of clocks for measuring the stability of fundamental constants. QSNET will include state-of-the-art atomic clocks, but will also develop next-generation molecular and highly charged ion clocks with enhanced sensitivity to variations of fundamental constants. We describe the technological and scientific aims of QSNET and evaluate its expected performance. We show that in the range of parameters probed by QSNET, either we will discover new physics, or we will impose new constraints on violations of fundamental symmetries and a range of theories beyond the Standard Model, including dark matter and dark energy models

High precision measurements of forbidden transitions in highly charged ions at the Heidelberg EBIT

Few-electron ions, which can be produced and studied at rest in electron beam ion traps (EBITs) are very well suited for the study of nuclear size effects and QED in strong fields, but the various contributions are usually entangled. Therefore, combinations of experiments with ions in different charge states are required to separate those contributions. In order to achieve this, several spectroscopic techniques have been recently implemented at the Heidelberg EBIT, aiming at high resolution and accuracy. In the optical region the most accurate wavelengths ever reported for highly charged ions [Draganic et al., Phys. Rev. Lett. 91 (2003) 183001] have been obtained, the results being sensitive to isotopic shifts [Tupitsyn et al., Phys. Rev. A 68 (2003) 022511] at the 0.01 meV level. The forbidden transitions of B-like ArXIV and Be-like ArXV ions studied here are especially interesting, since the QED contributions are as large as 0.2%. Improved atomic structure calculations allow to determine their values with growing accuracy, although the theoretical accuracy still lags three to four orders of magnitude behind the experimental one. In a different experiment, the lifetime of the corresponding metastable level has also been measured with an uncertainty of less than 0.2% thus becoming sensitive to the influence of the bound electron anomalous magnetic moment, an almost experimentally unexplored QED effect so far. A new laser spectroscopic setup aims at facilitating future studies of the hyperfine structure of heavy hydrogenic ions. Through the study of the dielectronic recombination, information on rare processes, such as two-electron-one-photon transitions in Ar16+ [Zou et al., Phys. Rev. A 67 (2003) 42703] at energies of around 2 keV, or the interference effects between dielectronic and radiative recombination in Hg77+ at 50 keV, and accurate values for the excitation energies of very heavy HCI have been obtained. A novel X-ray crystal spectrometer allowing absolute X-ray wavelength measurements in the range up to 15 keV with very high precision and reproducibility is currently used to study the Lyman series of H-like ions of medium-Z ions and the 2s-2p transitions of very heavy Li-like ions. (c) 2005 Elsevier B.V. All rights reserved.12th International Conference on the Physics of Highly Charged Ions, Sep 06-11, 2004, Vilnius, Lithuani

Single-electron capture in keV Ar15+...18++He collisions

Single-electron capture in 14 keV q(-1) Ar15+...18++He collisions is investigated both experimentally and theoretically. Partial cross sections and projectile scattering angle dependencies have been deduced from the target ion recoil momenta measured by the COLTRIMS technique. The comparison with close-coupling results obtained from a two-centre extension of the basis generator method yields good overall agreement, demonstrating the applicability of close-coupling calculations to collision systems involving highly charged ions in charge states up to 18+.FANTOM German Academic Exchange Servic