(Quasi)resonance electron-capture processes in non-symmetrical $(Z_{\rm P} \simeq 2Z_{\rm T})$ heavy ion-atom collisions are studied employing a semiclassical atomic Dirac-Fock-Sturm orbital coupled-channel approach within an independent-particle model. %A special attention has been paid to study a role of the relativistic effects. Systematic calculations of the electron-capture cross sections of the target $K$-shell electrons to the $L$ subshells of the projectile have been carried out for the collisions of bare thorium $(Z_{\rm P}=90)$ and zinc $(Z_{\rm P}=30)$ nuclei with hydrogenlike ions $(Z_{\rm T}=36$-$47)$ and $(Z_{\rm T}=12$-$15)$, correspondingly. Strong relativistic effects, crucial for the case of Th$^{90+}$-Ru$^{43+}(1s)$ collisions in the low-energy regime, are found. Various one- and two-electron capture processes occurring in course of the collisions of the two-electron system Th$^{90+}$-Ru$^{42+}(1s^2)$ have been investigated in details in the wide range of collision energies $0.5$-$50$~MeV/u. The impact parameter dependencies of the double electron-capture processes are also presented. Our study demonstrates a very significant role of the relativistic effects for the processes, which becomes crucial in the low-energy regime.
Interplay between relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics of Xe atoms
本文从理论上研究了重原子的X射线多光子电离动力学。当原子暴露于由X射线自由电子激光（XFEL）产生的强X射线脉冲时，它通过一系列单光子电离和伴随的弛豫过程电离成高电荷离子，并且其最终电荷状态受到可以通过单光子电离电离的最后离子状态的限制。如果X射线多光子电离涉及重原子中的深内壳层电子，则相对论效应引起的能量移动在电离动力学中起重要作用，如[Phys.\修订版本\ Lett. \textbf{110}，173005（2013）]。另一方面，如果X射线束具有宽的能量带宽，则高强度X射线脉冲可以驱动宽范围的离子状态的共振光激发，并且甚至超过直接单光子电离极限，如在[Nature\ Photon.]中首次提出的。\textbf{6}，858（2012）]。为了研究相对论和共振效应，我们扩展了\textsc{xatom}工具包，将相对论能量校正和共振激发在X射线多光子电离动力学计算。计算了光子能量分别为1.5keV和5.5keV的强流XFEL脉冲与双原子相互作用系统的电荷态分布。对于这两种光子能量，我们证明了共振激发的电离动力学的作用是改变由于轨道能级的相对论效应的显着移位。因此，要准确模拟高X射线强度下的多光子多重电离动力学，必须考虑这两种效应。
