Application of ATTOMESA to Ultrafast Electron Dynamics in Molecules

We present applications of the time-dependent quantum-chemistry framework ATTOMESA [1,2] to the study of ultrafast electron dynamics in atoms and molecules driven by intense and ultrashort laser pulses. The platform enables first-principles simulations of a broad range of ultrafast spectroscopies, including X-ray core-hole ionization, strong-field ionization, angle-resolved photoelectron spectroscopy, and high-harmonic generation (HHS). We focus on studies aimed at tracking excited-state electronic charge fluctuations in simple polyatomic molecules and probing their evolution using HHS and molecular-frame photoelectron angular distributions (MFPADs), and we briefly explore angle-resolved photoionization time delays associated with core-hole ionization in selected polyatomic systems. Together, these results illustrate how ATTOMESA provides a unified first-principles framework to model ultrafast electronic processes and experimentally accessible observables in molecular systems.

[1] Bondy et al., Phys. Rev. A 109, 043113 (2024).

[2] Hamer et al., Atoms 2025, 13 (11), 92.