A hybrid quantum-classical approach to the interaction of atomic clusters with intense laser fields in the vacuum ultra-violet (VUV) has been developed. Much emphasis is put on localized electrons, those quasi-free electrons which localize about the ions and screen them. These electrons set a time scale, which is used to interpolate between the quantum, rate based description of photon absorption by bound electrons and the classical, deterministic description of the cluster nano-plasma. Typical observables such as total energy absorption, electron and ion spectra are in very good agreement with the experimental findings. A scheme to probe the multi-electron motion in clusters with attosecond laser pulses is introduced. Conventional final state measurements in the energy domain cannot provide information about earlier states of the system due to the incoherent nature of the dynamics. Time-delayed attosecond pulses in the extreme ultra-violet (XUV) are used to probe the transient charging of the cluster ions during the interaction with the laser by measuring the kinetic energy of the electrons detached by the probe pulse. This information is otherwise lost at later times due to recombination. Knowledge about the transient charging would also shed more light on the still controversial subject of the energy absorption mechanisms in the VUV regime. Moving to shorter duration of the excitation, the characteristic time-scales for ionization and plasma equilibration are inversed. An attosecond laser pulse in the VUV regime creates a dense, warm nano-plasma far from equilibrium. Time-delayed attosecond pulses in the XUV probe then both the creation and the relaxation. The latter shows the breakup of the Bogoliubov hierarchy of characteristic times, indicating strongly-coupled plasma dynamics and drawing parallels to the relaxation of extended ultra-cold neutral plasmas with millions of particles.

In this work systematic studies of the organic semiconductor CuPc have been presented. In general the investigation can be devided in three parts. In the first one we have studied the electronic structure of clean CuPc thin film. The next two parts are devoted to organic-organic and metal–organic interface formation, where one of the interface components is CuPc thin film. The main results of this thesis are: - The electronic structure of the pristine organic semiconductor CuPc (valence band and empty states) has been obtained by a combination of conventional and resonant photoemission, near-edge X-ray absorption, as well as by theoretical ab initio quantum-chemical calculations. A qualitative assignment of different VB structures has been given, or in other words the contributions of different atomic species as well as sites of the CuPc molecule to the electronic DOS has been established. In particular, it was shown, that the HOMO is mainly comprised of the spectral weights from the orbitals of carbon pyrolle atoms. Additional contributions to the HOMO stems from the benzene atoms. A combined experimental and theoretical study of the unoccupied electronic density of states of CuPc was presented. Our study allows identifying the contributions from different parts of the molecule to the unoccupied DOS and the measured spectra, which lays grounds for future studies of the evolution of the CuPc electronic states upon e.g. functionalization or doping. Application of similar studies to other organic semiconductors will also provide significant insight into their unoccupied electronic states. - The electronic properties of the organic heterointerfaces between fullerite and pristine copper phthalocyanine were studied. Both interfaces, CuPc/C60 and C60/CuPc, were found to be non-reactive with pronounced shifts of the vacuum level pointing to the formation of an interfacial dipole mainly at the CuPc side of the heterojunctions. The dipole values are close to the difference of the work functions of the two materials. Important interface parameters and hole-injection barriers were obtained. The sequence of deposition does not influence the electronic properties of the interfaces. - CuPc doped with potassium was studied by means of photoemission and photoabsorption spectroscopy. A detailed analysis of the core-level PE spectra allows one to propose possible lattice sites, which harbor the potassium ions. Contrasting to a few results reported in the literature, the films prepared in this thesis showed no finite electronic density of states at the Fermi level. - Two stages of the In/CuPc interface formation have been distinguished. The low-coverage stage is characterized by a strong diffusion of the In atoms into the organic film. Metal ions occupy sites close to the pyrolle nitrogen and strongly interact with molecules transferring negative charge to CuPc. Indium diffusion into the organic films saturates at a stoichiometry of In2CuPc. Subsequently, in the second stage the formation of a metallic indium film occurs on the top of the In2CuPc film. - Upon deposition on CuPc film Sn and Ag atoms do not diffuse into the organic film forming metallic clusters and/or thin metallic overlayer. Sharp metal-organic film interface is formed, in contrast to indium and potassium deposition. Presented experimental results also give evidence for absence of noticeable chemical reaction of Sn and Ag with CuPc thin film. - The systematic investigation of interface formation between CuPc thin film and various metals gives us the possibility to summarize all results with demonstrating similarities and differences for all systems studied.