Chemical bonding patterns fundamentally change when molecules dynamically evolve in electronically excited states created by optical excitations. These dynamics give rise to various useful properties and functionalities, which are often investigated using time-resolved spectroscopic techniques. In this talk I will overview several applications of the Non-adiabatic EXcited-state Molecular Dynamics (NEXMD) framework, which was developed through collaboration across multiple institutions and has been released to the public. The NEXMD code is capable of simulating tens of picoseconds of photoinduced dynamics in large molecular systems, capturing the behavior of densely interacting and crossing excited states. n the first example, we utilize dynamical simulations to compute X-ray Raman signals, which allow us to monitor the coherence evolution in molecular photoswitches. Additionally, time-resolved X-ray diffraction provides further insight by probing key chemical features during the ultrafast dynamics. In the second example, we assess the excited-state photoinduced dynamics of a dendrimer and demonstrate on-the-fly simulations of its transient absorption pump-probe (TA-PP) spectra. These simulations reveal how the evolution of the TA-PP spectra tracks real-time photoinduced energy relaxation and redistribution, offering a detailed microscopic view of the underlying energy-transfer pathways.
1. V. M. Freixas, W. Malone, X. Li, H. Song, H. Negrin-Yuvero, A. White, T. R. Gibson, D. V. Makhov, D. V. Shalashilin, Y. Zhang, N. Fedik, M. Kulichenko, R. Messerly, L. N. Mohanam, S. Sharifzadeh, A. Bastida, S. Fernandez-Alberti, and S. Tretiak “NEXMD2 Software Package for Nonadiabatic Excited State Molecular Dynamics Simulations,” J. Chem. Theory Comput., 19, 5356 – 5368 (2023).
2. Y. Nam, H. Song, V. M. Freixas, S. Fernandez-Alberti, D. Keefer, Jin Yong, M. Garavelli, S. Tretiak, and S. Mukamel “Monitoring vibronic coherences and molecular aromaticity in photoexcited cyclooctatetraene with an X-ray probe: a simulation study,” Chem. Sci., 14, 2971 (2023).
3. V. M. Freixas, J. R. Rouxel, Y. Nam, S. Tretiak, N. Govind, S. Mukamel, “X‐ray and Optical Circular Dichroism as Local and Global Ultrafast Chiral Probes of [12]Helicene Racemization”, J. Am. Chem. Soc., 145, 21012 (2023)
4. R. Perez-Castillo, V. M. Freixas, S. Mukamel, A. Martinez-Mesa, L. Uranga-Piña, S. Tretiak, M. F. Gelin, and S. Fernandez-Alberti “Transient-Absorption Spectroscopy of Dendrimers via Nonadiabatic Excited-State Dynamics Simulations,” Chem. Sci., 15, 13250 – 13261 (2024).
5. B. Zhang, Y. Gu, V. M. Freixas, S. Sun, S. Tretiak, J. Jiang, and S. Mukamel “Cavity Manipulation of Attosecond Charge Migration in Conjugated Dendrimers,” J. Am. Chem. Soc., 146, 26743 – 26750 (2024).