<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="6.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Amaro, P</style></author><author><style face="normal" font="default" size="100%">Santos, J. P.</style></author><author><style face="normal" font="default" size="100%">Parente, F.</style></author><author><style face="normal" font="default" size="100%">Surzhykov, A.</style></author><author><style face="normal" font="default" size="100%">Indelicato, P.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Resonance effects on the two-photon emission from hydrogenic ions</style></title><secondary-title><style face="normal" font="default" size="100%">Physical Review A (Atomic, Molecular, and Optical Physics)</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">bound states</style></keyword><keyword><style  face="normal" font="default" size="100%">Dirac equation</style></keyword><keyword><style  face="normal" font="default" size="100%">quantum electrodynamics</style></keyword><keyword><style  face="normal" font="default" size="100%">radiative lifetimes</style></keyword><keyword><style  face="normal" font="default" size="100%">two-photon processes</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://link.aps.org/abstract/PRA/v79/e06250</style></url></web-urls></urls><number><style face="normal" font="default" size="100%">6</style></number><volume><style face="normal" font="default" size="100%">79</style></volume><pages><style face="normal" font="default" size="100%">062504</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A theoretical study of the all two-photon transitions from initial bound states with ni=2,3 in hydrogenic ions is presented. High-precision values of relativistic decay rates for ions with nuclear charge in the range 1&lt;=Z&lt;=92 are obtained through the use of finite basis sets for the Dirac equation constructed from B splines. We also report the spectral (energy) distributions of several resonant transitions, which exhibit interesting structures, such as zeros in the emission spectrum, indicating that two-photon emission is strongly suppressed at certain frequencies. We compare two different approaches (the line profile approach and the QED approach based on the analysis of the relativistic two-loop self-energy) to regularize the resonant contribution to the decay rate. Predictions for the pure two-photon contributions obtained in these approaches are found to be in good numerical agreement.</style></abstract></record></records></xml>