Description
Time-resolved photoelectron spectroscopy (TRPES) serves as a robust tool to probe evolving electronic structure during ultrafast molecular processes in the gas and liquid phases. Valence band TRPES has shown its capacity to follow conical intersection dynamics and excited-state relaxation processes [1]. Understanding these high coupling regions, e.g., conical intersections is key to predict and design chromophores with specific properties such as photoswitches. [2] X-ray TRPES, however, serves as a tool to spot transient species from a side-specific perspective.[3] Simulation of these processes remains a challenge for the nonadiabatic dynamics community, especially for large molecules where high accuracy methods become unaffordable. For that reason, we developed and tested a computational workflow for simulating time-resolved photoemission signals using mixed-reference spin-flip TDDFT combined with an extended Koopmans theorem treatment of ionization (MRSF-TDDFT/EKT). [4,5,6] The approach provides binding energies and Dyson-orbital-based ionization intensities for transient molecular geometries at modest additional cost, making it suitable for post-processing nonadiabatic trajectory ensembles and for direct comparison with TRPES observables. The framework was then applied to ethylene and stilbene, demonstrating that MRSF-TDDFT/EKT can reproduce the main low-energy valence TRPES features and can also provide site-sensitive carbon K-edge TRXPS signatures of structural distortions such as twisting and charge polarization. The results show that the method is a practical tool for connecting nonadiabatic dynamics with experimentally measurable photoelectron spectra, while also emphasizing the need for prior validation of the relevant ionization-energy window.
[1] List, N. H., Jones, C. M. Martínez, T. J. Chem. Sci., 2022, 13,373.
[2] A. Stolow, A. E. Bragg and D. M. Neumark, Chem. Rev., 2004, 104, 1719–1757.
[3] I. Gabalski et al., J. Phys. Chem. Lett., 2023, 14, 7126–7133.
[4] H. Huang, J. Zhang, D. Hu and Y-J Liu, J. Phys. Chem. Lett. 2025.
[5] V. Pomogaev, S. Lee, S. Shaik, M. Filatov and C. H. Choi, J. Phys. Chem. Lett., 2021, 12, 99639972.
[6] W. Park, M. Alías-Rodríguez, D. Cho, S. Lee, M. Huix-Rotllant, M. Filatov and C. H. Choi, J. Chem. Theory Comput., 2022, 18, 6240–6250.
