On the Emergence of Spin-Orbit Dynamics in Sudden Ionization 

Advancements in ultrafast laser techniques have established the study of electronic dynamics as a central pillar of modern AMO physics. Describing the dynamics of ionization in many-electron atoms and molecules has been a long-standing challenge that has been tackled using different theoretical frameworks. One such approach is the sudden approximation, in which an electron is instantaneously removed from the system, causing the rearrangement of the remaining electrons in response to the change in the charge screening. In this work, we develop an extension to the sudden approximation where an electron is placed in a quasi-continuum while accounting for its interaction with the remaining electrons of the system. We investigate the time scale over which the rearrangement of the leaving and the remaining electrons gives rise to the spin-orbit splitting and explore the impact that parameters such as the energy of the photoelectron and the intensity of the ionizing pulse have on this process. We present a simple model that captures the physics of ionization and emphasizes the role of spin-orbit coupling in the dynamics. We apply our approach to simulate the ionization in the argon atom, identifying specific pulse characteristics required to induce and maximize the electronic coherences within the residual ion.