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Cluster studies in molecular beams
Profant, Václav ; Kužel, Petr (referee) ; Dian, Juraj (advisor)
In the present work we study properties of clusters of small heteroatomic molecules with biological relevance by several experimental methods based on molecular beams. In the rst experiment structure and dynamics of size-selected charged pyrrole clusters have been studied by means of molecular beam scattering experiment. Small neutral P yn clusters were produced in Py/He expansions and larger mixed P ynArm clusters in Py/Ar expansions, and the scattering experiment with a secondary beam of He atoms was used to select the neutral clusters of dierent sizes. The complete size-selected fragmentation patterns for the neutral dimer to tetramer after an electron impact ionization at 70 eV from the measurements of the angular and velocity distributions at dierent fragment masses. In second experiment photolysis of size selected pyrrole, imidazole and pyrazole clusters has been investigated. Comparison with the photolysis of an isolated molecules and between studied systems has been made. Clusters were photolyzed at 243 and 193 nm and the kinetic energy distributions of the H-photofragments have been measured and analyzed. Finally the mass spectra of the fragments after multiphoton ionization have been measured. The signicant inuence of the cluster environment to the photolytic behavior was observed and discussed.
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Laser photolysis of molecules in free nanoparticles
Tkáč, Ondřej ; Dian, Juraj (advisor) ; Kužel, Petr (referee)
Several experiments with various clusters were performed on a molecular beam apparatus. (1) The beam velocities were measured for rare gases and water clusters under various expansion conditions to learn about the supersonic expansions and cluster generation processes. (2) The photodissociation of (HBr)n clusters was measured for calibration purposes. (3) The mass spectrometry of clusters of small biomolecules imidazole, pyrazole and pyrrole was investigated. The stabilization of these hydrogen bonded species in the excited states by hydrogen transfer process was revealed, relevant to the stability of biomolecules in general. (4) Finally, the photodissociation of an HI molecule on water clusters (H2O)n was studied and compared to the photodissociation on (Ar)n clusters. It was shown that HI molecules acidically dissociate on (H2O)n and generate zwitterionic species H3O+ I-(H2O)n-1, which are then excited into biradical states with the neutral hydronium molecule H3O.
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Application of metamaterial structures in terahertz spectral range
Šibík, Juraj ; Kužel, Petr (advisor) ; Čtyroký, Jiří (referee)
The thesis is devoted to a research on metamaterials for terahertz spectral range based on deeply etched silicon. The aim of the work is a theoretical conception and experimental realization of wave plates for selected terahertz frequencies. These wave plates are made of silicon substrates with an etched two-dimensional periodic microstructure where the dimensions of an elementary cell are below the considered wavelength. Theoretical proposal is optimized using the transfer matrix formalism. We designed and experimentally characterized quarter-wave plates for frequencies 0.5 THz and 1 THz and a half-wave plate for frequency 1 THz.
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Time-Resolved Terahertz Spectroscopy Applied to the Investigation of Magnetic Materials and Photonic Structures
Němec, Hynek ; Kužel, Petr (advisor) ; Čtyroký, Jiří (referee) ; Crozat, Paul (referee)
Two distinct branches of optics are combined in this work: Time-domain terahertz spectroscopy, and photonic structures. The work at rst provides a survey of tools utilized for exploration of the terahertz region, and it enriches them by a method for simultaneous determination of dielectric and magnetic response of materials and metamaterials. Photonic structures operating in the terahertz range form the subject of the rest of this thesis. A periodically modulated dielectric waveguide is studied theoretically using a modal method: The band structure of guided and leaky modes is calculated and resonant modes are described. One-dimensional photonic crystals with a defect are then investigated in detail. Formation of defect modes is analyzed theoretically in a photonic crystal with a twinning defect. The analysis makes it possible to formulate requirements on a design of a structure with defect modes tunable by external parameters. Following these guidelines, we have successfully designed, fabricated and characterized photonic crystals with thermally tunable defect modes with relative tunability reaching 60 %.
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Temporal Prediction in the Work of Pavel Tichý
Kužel, Petr
The paper deals with temporal prediction within a theoretical system of transparent intentional logic of Czech logician Pavel Tichy. Article in a nutshell characterizes Tichy's arguments against atemporal or time-less conception of Bertrand Russell. It shows how on base of temporal prediction is possible to overcome some logical paradoxes. Explicitly is treated for example McTaggart's paradox.
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