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Röder, Anja

Publications and source records attributed to Röder, Anja.

3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

X-ray induced Coulomb explosion imaging of transient excited-state structural rearrangements in CS2

Abstract Structural imaging of transient excited-state species is a key goal of molecular physics, promising to unveil rich information about the dynamics underpinning photochemical transformations. However, separating the electronic and nuclear contributions to the spectroscopic observables is challenging, and typically requires the application of high-level theory. Here, we employ site-selective ionisation via ultrashort soft X-ray pulses and time-resolved Coulomb explosion imaging to interrogate structural dynamics of the ultraviolet photochemistry of carbon disulfide. This prototypical system exhibits the complex motifs of polyatomic photochemistry, including strong non-adiabatic couplings, vibrational mode couplings, and intersystem crossing. Immediately following photoexcitation, we observe Coulomb explosion signatures of highly bent and stretched excited-state geometries involved in the photodissociation. Aided by a model to interpret such changes, we build a comprehensive picture of the photoinduced nuclear dynamics that follows initial bending and stretching motions, as the reaction proceeds towards photodissociation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Core spectroscopy of oxazole

We have measured, analyzed and simulated the ground state valence photoelectron (PES), X-ray absorption (XAS), X-ray photoelectron (XPS) as well as normal and resonant Auger-Meitner electron (AES) spectra of oxazole at the carbon, oxygen and nitrogen K-edge in order to understand its electronic structure. Experimental data is compared to theoretical calculations performed at the coupled cluster, restricted active space perturbation theory to second order and time-dependent density functional levels of theory. We demonstrate that both N and O K-edge XAS are sensitive to the amount of dynamical electron correlation included in the theoretical description, and that for a complete description of XPS, additional orbital correlation and orbital relaxation effects need to be considered. The normal AES are dominated by a singlet excitation channel and well described by theory. Furthermore, the resonant AES, however, are more complicated. While the participator decay channels, dominating at higher kinetic energies, are well described by coupled cluster theory, spectator channels can only be described satisfactorily using a method that combines restricted active space perturbation theory to second order for the bound part and a one-center approximation for the continuum.

74 ATOMIC AND MOLECULAR PHYSICS↗