Time-resolved XUV photoelectron-photoion coincidence spectroscopy

Abstract

The possibility to produce ultrashort light pulses with pulse durations in the femtosecond and attosecond time scale (currently even down to a pulse length of 43as [1]) has triggered a worldwide eort of research on time-resolved measurements of electronic dynamics [2, 3, 4] in atoms, molecules [5] and, since very recently, even in solids [6]. For molecules, restructuring of the electronic system induces nuclear dynamics such as the breakage of a chemical bond, which is the primary process of any chemical reaction. In order to study processes like photoionization or photodissociation, measurement techniques needed to be developed, giving us more insight into those processes. One such technique is Photoelectron-Photoion Coincidence Spectroscopy (PEPICO) where the energies of electrons and the mass-to-charge ratio of ions emerging from the interaction of a molecule with an ultrashort light pulse are measured in coincidence. This approach adopted in a time-resolved manner to a pump-probe scheme has already shown great results like direct observation of photochemical activation energy in acetone [7], discovering electronic shake-up in molecular fragmentation processes [8] or the detection of Feshbach resonances [9]. The motivation for this diploma thesis is the eort to implement and test the possibility for PEPICO measurements in an attosecond XUV beamline equipped with a single time-of- ight mass spectrometer. The implementation was enabled by developing a fast high-voltage electrical switch, which permits switching from 0 to 2kV within a sub-100 nanosecond duration synchronously with the kHz repetition rate of the laser pulse used for PEPICO measurements, and by developing a suitable software for triggering, data read-out and data visualization during the experiment.