Interferometry on small quantum systems at short wavelength

Abstract

The present work concentrates on prototypical studies of light-induced correlated manybodydynamics in complex systems. In its course a reflective split-and-delay unit (SDU)for phase-resolved one-color pump-probe experiments with gas phase samples using VUV–XUV laser pulses was built. The collinear propagation of pump and probe pulses is ensuredby the special geometry of the SDU and allows to perform phase-resolved (coherent)autocorrelation measurements. The control of the pump-probe delay with attosecondprecision is established by a specially developed diagnostic tool based on an in-vacuumwhite light interferometer that allows to monitor the relative displacement of the SDU reflectorswith nanometer resolution. Phase-resolved (interferometric) pump-probe experimentswith developed SDU require spatially-resolved imaging of the ionization volume.For this an electron–ion coincidence spectrometer was built. The spectrometer enablescoincident detection of photoionization products using velocity map imaging (VMI) techniquefor electrons and VMI or spatial imaging for ions. In first experiments using thedeveloped SDU and the spectrometer in the ion spatial-imaging mode linear field autocorrelationof free-electron laser pulses at the central wavelength of 38 nm was recorded.A further focus of the work were energy- and time-resolved resonant two-photonionization experiments using short tunable UV laser pulses on C60 fullerene. The experimentsdemonstrated that dipole-selective excitation on a timescale faster than thecharacteristic intramolecular energy dissipation limits the number of accessible excitationpathways and thus results in a narrow resonance. Time-dependent one-color pumpprobestudy showed that nonadiabatic (vibron) coupling is the dominant energy dissipationmechanism for high-lying electronic excited states in C60

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