José Paulo Santos
Professor Catedrático do Departamento de Física da FCT/UNL
DF - FCT NOVA, Quinta da Torre, 2829 -516 MONTE DA CAPARICA , PORTUGAL (email)
DF - FCT NOVA, Quinta da Torre, 2829 -516 MONTE DA CAPARICA , PORTUGAL (email)
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 2s1/2–>1s1/2 and 2p1/2–>1s1/2 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.