Testing fundamental interactions on the helium atom

Testing fundamental interactions on the helium atom We critically examine the current status of theoretical calculations of the energies, the fine structure, and the isotope shift of the lowest-lying states of helium, searching for unresolved discrepancies with experiments. Calculations are performed within the quantum electrodynamics expansion in powers of the fine structure constant α and the electron-to-nucleus mass ratio m/M. For energies, theoretical results are complete through orders α6m and α6m2/M, with the resulting accuracy ranging from 0.5 to 2 MHz for the n=2 states. The fine-structure splitting of the 2P3 state is predicted with a much better accuracy, 1.7 kHz, as a consequence of a calculation of the next-order α7m effect. An excellent agreement of the theoretical predictions with the recent measurements of the fine structure provides one of the best tests of the bound-state QED in few-electron systems. The isotope shift between He3 and He4 is treated with a subkilohertz accuracy, which allows for a high-precision determination of the differences of the nuclear charge radii δr2. Several such determinations, however, yield results that are in a 4σ disagreement with each other, which remains unexplained. Apart from this, we find no significant discrepancies between theory and experiment for the helium atom. A further calculation of the yet unknown α7m correction to energy levels will provide a sensitive test of universality in electromagnetic interactions of leptons by comparison of nuclear charge radii obtained by the helium and muonic helium spectroscopy. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review A American Physical Society (APS)

Testing fundamental interactions on the helium atom

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Testing fundamental interactions on the helium atom

Abstract

We critically examine the current status of theoretical calculations of the energies, the fine structure, and the isotope shift of the lowest-lying states of helium, searching for unresolved discrepancies with experiments. Calculations are performed within the quantum electrodynamics expansion in powers of the fine structure constant α and the electron-to-nucleus mass ratio m/M. For energies, theoretical results are complete through orders α6m and α6m2/M, with the resulting accuracy ranging from 0.5 to 2 MHz for the n=2 states. The fine-structure splitting of the 2P3 state is predicted with a much better accuracy, 1.7 kHz, as a consequence of a calculation of the next-order α7m effect. An excellent agreement of the theoretical predictions with the recent measurements of the fine structure provides one of the best tests of the bound-state QED in few-electron systems. The isotope shift between He3 and He4 is treated with a subkilohertz accuracy, which allows for a high-precision determination of the differences of the nuclear charge radii δr2. Several such determinations, however, yield results that are in a 4σ disagreement with each other, which remains unexplained. Apart from this, we find no significant discrepancies between theory and experiment for the helium atom. A further calculation of the yet unknown α7m correction to energy levels will provide a sensitive test of universality in electromagnetic interactions of leptons by comparison of nuclear charge radii obtained by the helium and muonic helium spectroscopy.
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Publisher
The American Physical Society
Copyright
Copyright © ©2017 American Physical Society
ISSN
1050-2947
eISSN
1094-1622
D.O.I.
10.1103/PhysRevA.95.062510
Publisher site
See Article on Publisher Site

Abstract

We critically examine the current status of theoretical calculations of the energies, the fine structure, and the isotope shift of the lowest-lying states of helium, searching for unresolved discrepancies with experiments. Calculations are performed within the quantum electrodynamics expansion in powers of the fine structure constant α and the electron-to-nucleus mass ratio m/M. For energies, theoretical results are complete through orders α6m and α6m2/M, with the resulting accuracy ranging from 0.5 to 2 MHz for the n=2 states. The fine-structure splitting of the 2P3 state is predicted with a much better accuracy, 1.7 kHz, as a consequence of a calculation of the next-order α7m effect. An excellent agreement of the theoretical predictions with the recent measurements of the fine structure provides one of the best tests of the bound-state QED in few-electron systems. The isotope shift between He3 and He4 is treated with a subkilohertz accuracy, which allows for a high-precision determination of the differences of the nuclear charge radii δr2. Several such determinations, however, yield results that are in a 4σ disagreement with each other, which remains unexplained. Apart from this, we find no significant discrepancies between theory and experiment for the helium atom. A further calculation of the yet unknown α7m correction to energy levels will provide a sensitive test of universality in electromagnetic interactions of leptons by comparison of nuclear charge radii obtained by the helium and muonic helium spectroscopy.

Journal

Physical Review AAmerican Physical Society (APS)

Published: Jun 27, 2017

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