Two-photon atomic level widths at finite temperatures

TL;DR

This paper calculates the thermal two-photon level broadening in hydrogen and helium-like ions using quantum electrodynamics, revealing a significant contribution from blackbody radiation that surpasses other known corrections and effects.

Contribution

It provides a rigorous QED-based calculation of thermal two-photon level widths at finite temperatures, highlighting a novel blackbody radiation-induced broadening effect.

Findings

Thermal two-loop correction can exceed relativistic and radiative QED corrections.

Blackbody radiation induces a level broadening different from stimulated decay and Raman scattering.

The effect surpasses the ordinary stimulated one-photon depopulation rate at laboratory temperatures.

Abstract

The thermal two-photon level broadening of the excited energy levels in the hydrogen and H-like helium is evaluated via the imaginary part of thermal two-loop self-energy correction for bound electron. All the derivations are presented in the framework of rigorous quantum electrodynamic theory at finite temperatures and are applicable for the H-like ions. On this basis, we found a contribution to the level broadening induced by the blackbody radiation which is fundamentally different from the usual line broadening caused by the stimulated two-photon decay and the Raman scattering of thermal photons. Numerical calculations of the two-loop thermal correction to the two-photon width for the $2s$ state in hydrogen and singly ionized helium atoms show that the effect could significantly exceed the higher-order relativistic and radiative QED corrections commonly included in the calculations. In addition, the thermal two-loop self-energy correction significantly exceeds the "ordinary" stimulated one-photon depopulation rate at the relevant laboratory temperatures. In this work, detailed analysis and the corresponding comparison of the effect with the existing laboratory measurements in H-like ions are carried out.