Title:	Deciphering light-induced processes in molecular systems
DNr:	NAISS 2026/3-250
Project Type:	NAISS Medium
Principal Investigator:	Nanna Holmgaard List <nanna.h.list@gmail.com>
Affiliation:	Kungliga Tekniska högskolan
Duration:	2026-04-01 – 2026-10-01
Classification:	10407
Homepage:	http://www.nhlist-lab.com/
Keywords:

Abstract

Photoinduced processes underpin a wide range of technologies, including photovoltaics, photocatalysis, molecular imaging, and emerging quantum technologies. This project aims to decipher the fundamental mechanisms governing light-driven transformations in molecular systems through large-scale quantum molecular dynamics simulations and calculations of their spectroscopic signatures. By combining nonadiabatic dynamics with simulations of electron, optical, and X-ray spectroscopies, we establish direct connections between theory and experiment in order to extract mechanistic insight from ultrafast measurements. A central component of the project is the interpretation of time-resolved X-ray experiments on prototype photochemical systems performed in collaboration with experimental partners at SLAC National Accelerator Laboratory. Using ab initio multiple spawning dynamics together with simulations of X-ray absorption, photoelectron, and scattering observables, we investigate ultrafast excited-state processes such as excited-state hydrogen transfer and the competition between internal conversion and intersystem crossing pathways. Beyond gas-phase systems, the project addresses photoinduced dynamics in complex molecular environments. We investigate mutation-dependent conformational heterogeneity in photo-switchable fluorescent proteins through enhanced-sampling molecular dynamics combined with QM/MM excited-state simulations. These studies aim to uncover how structural fluctuations and protonation microstates modulate excited-state pathways, providing design principles for improved biomarkers and optogenetic tools. In parallel, we expand the scope of the project toward molecular materials for sustainable energy and quantum technologies. First, we investigate excited-state dynamics and charge-transfer processes in molecular building blocks relevant for photocatalytic polymers in order to identify the molecular factors controlling photoredox activity. Second, we develop theoretical models to understand spin-dependent photoinduced electron and energy transfer in chiral donor-bridge-acceptor systems, motivated by recent discoveries in chirality-induced spin selectivity and their potential relevance for molecular spin-based quantum technologies. Methodologically, we extend our benchmarking and development of multiconfigurational density-functional theory approaches, including MR-SFTDDFT and variational MC-PDFT, as electronic-structure engines for nonadiabatic dynamics simulations. Together, these efforts combine methodological development, large-scale simulations, and experiment-theory integration to uncover general design principles for light-driven molecular function.