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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:00 |
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Conference: Bucharest University Faculty of Physics 2002 Meeting
Section: Optics, Spectroscopy, Plasma and Lasers
Title:
QED-Sensitive Measurement of
The 2s2p 3P1-2s2 1S0 Transition Energy in Be-like Ag
Authors:
Corneliu Catalin Neacsu, Valentin Barna
Affiliation:
University of Bucharest, Faculty of Physics
E-mail
Keywords:
Abstract:
Experimental studies of atomic energy levels are usually performed by applying an excitation-mechanism to the atoms or ions, determining the energies and intensities of the de-excitation radiation.
The fundamental theory of the electromagnetic interaction, suitable to study the atomic structure, is the Quantum Electrodynamics (QED).
According to Dirac’s theory, an energy degeneracy results in hydrogen atom for the states with the same angular momentum j, but the experiments contradicted that. Lamb stated that between 2s2S1/2 and 2p2P1/2 levels there is an energy difference - The Lamb-Shift (QED effects). The leading contributions of the QED effects are self-energy and vacuum-polarization
The three and four-electron systems gain increasing importance, especially for high Z (perturbation treatments are no more valid), due to the leading QED contribution to the energy levels.
We measured the wavelength of the 2s2p 3P1-2s2 1S0 intercombination-transition in beryllium-like Ag, this being the first precise measurement ever.
The experiment was performed at the UNILAC-Accelerator in GSI-Darmstadt using Beam-Foil Spectroscopy on the 5m Grazing-Incidence VUV Spectrometer. The wavelength calibration was performed in-situ using an accurate Penning-discharge lamp.
The obtained accuracy of 74ppm (2x10-3 of the total QED contribution) makes the experimental result precise enough for comparison with the last calculations and can initiate more sophisticated advances.
The measured energy shows a good agreement with the Relativistic Many-Body Perturbation Theory. Concerning the Configuration-Interaction method, a deviation from experiment results.
The experiment can decide between the two calculations, those being the only calculations that include QED contributions to the total transition-energy for the Be-like ions. Nevertheless, this is not a support for the RMBPT, since a closer inspection of both calculations shows differences in the correlation-energies and in the QED contribution.
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