Rostock 2019 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 8: XUV and X-ray Excitation and Spectroscopy
MO 8.3: Vortrag
Montag, 11. März 2019, 16:45–17:00, S HS 001 Biologie
Femtosecond dynamics in highly excited neutral CO2: an experimental and theoretical study — •Thomas Schnappinger1, Matteo Lucchini2, Mario Murari2, Giacinto D. Lucarelli2, Luca Poletto2, Fabio Frassetto2, Mauro Nisoli2, and Regina de Vivie-Riedle1 — 1Department of Chemistry, LMU Munich, Germany — 2Physics Department, Politecnico di Milan, Italy
The idea of this work is to combine an extreme UV (XUV) pulse and a few-femtosecond IR pulse in a pump-probe approach on carbon dioxide molecules. Here we want to present the first theoretical results obtained to interpret the experimental findings.
The dominant, almost constant, signal in the time dependent photoelectron spectrum arises from the direct ionization of the molecule just by the XUV pulse. A weaker oscillating signal with lower kinetic energy is also detected. The fastest observed period is around 28 fs.
Using high-level multi-reference methods (CASSCF and CASPT2) we are able to determine the electronic states of carbon dioxide in an energy range from 0 to 20 eV. Calculating the potential energy surfaces of various states it is possible to locate bound neutral states in the vicinity of the ionization threshold. The information of the static calculations in combination with the experimental results offers an interpretation of the weaker oscillating signal. The observed oscillation can be attributed to the vibrational motion of the nuclear wave packet in highly excited states around 1 eV below the ionization threshold.