The process of a positron $\unicode{x2013}$ bound-electron annihilation with simultaneous emission of two photons is investigated theoretically. A fully relativistic formalism based on $\textit{ab initio}$ QED description of the process is worked out. The developed approach is applied to evaluate the annihilation of a positron with $K$-shell electrons of a silver atom, for which a strong contradiction between theory and experiment was previously stated. The results obtained here resolve this long-standing disagreement and, moreover, demonstrate a sizeable difference with approaches so far used for calculations of the positron $\unicode{x2013}$ bound-electron annihilation process, namely, the $\textit{Lee's}$ and $\textit{impulse}$ approximations.
A new ab initio method of calculating $Z_{eff}$ and positron annihilation rates using coupled-channel T-matrix amplitudes
本文提出了一种新的计算$Z_{eff}$和正电子湮没率的{ \it ab initio}理论公式，它利用在壳层和半离壳层T矩阵散射振幅，而不直接使用散射波函数。只要系统的动力学可以用Lippmann-Schwinger型方程描述，该公式就具有精确性和普适性。它可以作为一个有效的工具，因为所有的$T-$，$K-$，和$S-$矩阵公式，直接产生的散射振幅，而不是波函数。我们还提出了一个基本的数值试验的制定。
Self-energy corrections to the ionization energies in sodium-like ions: comparison of the \textit{ab initio} QED and model-QED-operator approaches
Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences（中国科学院精密测量科学与技术创新学院）；University of Chinese Academy of Sciences（中国科学院大学）；Department of Physics, St. Petersburg State University（圣彼得堡国立大学物理系）；Petersburg Nuclear Physics Institute named by B.P. Konstantinov of National Research Center “Kurchatov Institute”（库尔恰托夫国家研究中心B.P.康斯坦丁诺夫彼得堡核物理研究所）；School of Physics and Engineering, ITMO University（ITMO大学物理与工程学院）
