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Abstract:
Within this thesis, molecular dynamics of diatomic molecules is studied
using the XUV–IR pump–probe technique. Here, a single extreme ultraviolet (XUV)
photon created by high-harmonic generation ionizes the diatomic target molecule.
The initiated dynamics is probed after a variable time delay by an ultrashort (12 fs)
infrared (IR) laser pulse. The 3-dimensional momenta of all charged fragments are
measured using a reaction microscope.
In an experiment on O2, a nuclear wave-packet oscillation is observed on the binding
potential-energy curve (PEC) of the O2+(a 4Πu) electronic state. By comparing
simulated results with experimental data, theoretically predicted PECs are tested.
The experimental results are best reproduced if the wave packet is propagated on a
Morse potential adjusted to the experimental data. This demonstrates the sensitivity
of our method and its ability to predict accurate PECs from the measured wave-packet
evolution.
In an N2 experiment, the pump–probe delay dependent yield of stable N2++ is observed.
It is interpreted as a sequential double ionization via a highly excited antibonding
cationic state. The dissociation of the intermediate state is temporally resolved
and can be interrupted by multi-photon ionization with the IR pulse within ≈ 15 fs
after XUV ionization.
