Freiburg 2024 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 16: Ultrafast Dynamics I
MO 16.2: Vortrag
Mittwoch, 13. März 2024, 14:45–15:00, HS 3044
Probing ultrafast nonadiabatic dynamics of NO2 with time-resolved X-ray absorption spectroscopy at N K-edge — •Lorenzo Restaino1, Zhuan-Yang Zhang2, Michael Coates1, Michael Odelius1, Markus Kowalewski1, Erik T. J. Nibbering2, and Arnaud Rouzé2 — 1Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden — 2Max-Born-Institute, Max-Born-Str. 2A, 12489 Berlin, Germany
Time-resolved X-ray absorption spectroscopy (tr-XAS) is a chemically sensitive method well-suited for investigating the intricate behavior of electronically excited molecules. We employed tr-XAS to explore the ultrafast nonadiabatic processes occurring at the conical intersection (CI) between the electronic ground and first excited state of nitrogen dioxide. Despite the success of the experimental tr-XAS spectrum in revealing photodissociation, its capacity to capture the CI dynamics was hindered by the restricted temporal resolution of the 60 fs UV pump pulse. To overcome this constraint, we performed high-level quantum dynamics simulations with a shorter pump pulse, allowing us to access the complex nonadiabatic relaxation events. In our study, an 8-fs UV pump pulse at 400 nm excited the system from the ground state, followed by a 1-fs Gaussian probe pulse at the nitrogen K-edge to probe the core-hole states. By using this temporally resolved pump, we were able to map the system’s passage through the conical intersection, identified through a spectral signature indicative of wave packet bifurcation. Consequently, we achieved a detailed tracing of the NO+O dissociation process.
Keywords: Time-resolved X-ray absorption; conical intersections; quantum wave packet dynamics; nonlinear X-ray spectroscopy