### Abstract

Two-photon decay of hydrogenlike ions is studied within the framework of second-order perturbation theory, based on the relativistic Dirac's equation. Special attention is paid to the effects arising from the summation over the negative-energy (intermediate virtual) states that occur in such a framework. In order to investigate the role of these states, detailed calculations have been carried out for the 2 s1/2 →1 s1/2 and 2 p1/2 →1 s1/2 transitions in neutral hydrogen H as well as for hydrogenlike xenon Xe53+ and uranium U91+ ions. We found that for a correct evaluation of the total and energy-differential decay rates, summation over the negative-energy part of Dirac's spectrum should be properly taken into account both for high- Z and low- Z atomic systems.

Original language | English |
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Article number | 052511 |

Journal | Physical Review A - Atomic, Molecular, and Optical Physics |

Volume | 80 |

Issue number | 5 |

DOIs | |

Publication status | Published - 30 Nov 2009 |

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## Cite this

*Physical Review A - Atomic, Molecular, and Optical Physics*,

*80*(5), [052511]. https://doi.org/10.1103/PhysRevA.80.052511