Thema der Dissertation:
Probing photoexcitation dynamics in molecules by ultrafast soft X-ray absorption spectroscopy at the nitrogen K-edge
Probing photoexcitation dynamics in molecules by ultrafast soft X-ray absorption spectroscopy at the nitrogen K-edge
Abstract: This thesis explores the development and application of ultrafast soft X-ray absorption spectroscopy (XAS) at the nitrogen K-edge to resolve fundamental molecular dynamics in both the gas and liquid phases. Utilising a laboratory-based high-order harmonic generation (HHG) source driven by infrared pulses (centered around 1800 nm) produced by a Ti:Sa laser amplifier coupled with an optical parametric amplifier, an experimental apparatus was implemented to produce broadband soft X-ray pulses between 200 and 450 eV. The capability of this table-top setup was first demonstrated by investigating the photodissociation and early conical intersection dynamics of gaseous NO_2 following single-photon excitation. The result highlights the sensitivity of transient X-ray absorption spectroscopy in probing the wave packet motion near the conical intersection. The research was further extended to the condensed phase using a novel liquid flat-jet system to study the charge transfer process of complex [Fe(bpy)_3]^{2+} in solution phase. By probing the nitrogen K-edge, this work provides the first femtosecond-resolved observation of the ligand's local electronic environment during metal-to-ligand charge transfer (MLCT). The result uniquely benchmarks the MLCT state signature both spectrally and temporally, offering new insights into the involved intermediate states that govern the efficiency of charge separation in transition metal complexes.
Zeit & Ort
24.07.2026 | 13:00
Hörsaal A (1.3.14)
(Fachbereich Physik, Arnimallee 14, 14195 Berlin)