Resonant effects on the two-photon emission from hydrogenic ions

TL;DR

This paper provides high-precision calculations of two-photon decay rates and spectral distributions for hydrogenic ions, revealing resonant suppression effects and comparing two regularization methods.

Contribution

It introduces a comprehensive theoretical analysis of two-photon transitions in hydrogenic ions using advanced relativistic methods and compares two approaches for handling resonances.

Findings

Spectral distributions show zeroes indicating suppressed emission at certain frequencies.

High-precision decay rates are obtained for ions with Z from 1 to 92.

Two different regularization approaches yield consistent results.

Abstract

A theoretical study 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 =< Z =< 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 zeroes in the emission spectrum, indicating that two-photon emission is strongly suppressed at certain frequencies. We compare two different approaches (the Line Profile Approach (LPA) and the QED approach based on the analysis of the relativistic two-loop self energy (TLA)) 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 a good numerical agreement.