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Radiative processes of small molecules
Šimsová, Martina ; Soldán, Pavel (advisor) ; Čurík, Roman (referee) ; Kalus, René (referee)
Four types of astrochemically relevant radiative processes are studied: bound-bound, bound-free, free-bound and free-free. The former two together determine radiative lifetimes, which are calculated for the HeLi+ molecular ion. Free-bound processes, also called radiative association, are studied on two systems: He in collisions with Li+ , and O in collision with C+. Collisions of He and Li+ are believed to have occurred during the recombination era of the Universe, while collisions of O with C+ are considered to be relevant in SN 1987A. Altogether, 17 radiative association cross sections and rate coefficients are calculated for radiative association, and the effect of a stimulated emission is also illustrated. A free-free process, also called radiative charge transfer, is studied in collisions of He with Li+.
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Quantum dynamics of small molecules
Augustovičová, Lucie ; Soldán, Pavel (advisor) ; Čurík, Roman (referee) ; Fišer, Jiří (referee)
This thesis deals with the process of molecular ions formation in interstellar space, which played an important role in the early Universe. A large part of the work focuses on the theoretical study of quantum dynamics of the process of radiative association pre- dominantly induced by dipole transitions. The effect of quadrupole transitions on the radiative association have also been taken into account, which has been studied for the first time. Furthermore, spectroscopic characteristics of rovibronic transitions of selected di- atomic ions for the study of cosmological variability of fundamental constants were determined. The main outcomes of the thesis include the characterization of depopulation of metastable levels He (23S) and He (21S) due to radiative collisions with hydrogen, helium and lithium ions, i. e. He + A+ → HeA+ + hν. Within the study quantum dynamics calculations were carried out using a fully quan- tal approach. Studied spontaneous and stimulated processes on a specific spin manifold were characterized by energy-dependent cross sections and temperature-dependent rate coefficients. Compared to previous published works by other authors highly excited electronic states are considered. The results showed that a) the spontaneous radiative association contributes significantly to the...
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Low-energy processes in H + H- collision
Eliášek, Jiří ; Čížek, Martin (advisor) ; Čurík, Roman (referee) ; Skála, Lubomír (referee)
In this work we generalize existing theory of low-energy collisions of atomic hydrogen with its anion. We extend the non-local resonance model for this system by adding new discrete state and two continua that are coupled with it. We calculate numerically cross sections for associative electron detachment process that is important for models of early universe. We add cross section for collision detachment and show spectra of outgoing electrons. We show how the isotopic effect is involved in studied collision. We also calculate charge transfer, elastic scattering cross sections, and reaction rates for hydrogen collisions with deuterium anion. We compare our results with recent experiments and we discuss their reliability. Powered by TCPDF (www.tcpdf.org)
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Modeling the dissociative recombination of light ions
Hvizdoš, Dávid ; Čurík, Roman (advisor) ; Kaprálová-Žďánská, Petra R. (referee) ; Kokoouline, Viatcheslav (referee)
The purpose of this work and the project under which it was created is to develop, compare and validate several theoretical approaches and computation methods used to calculate the cross sections of dissociative recombination. For the most part it is con- cerned with the indirect dissociative recombination of molecular ions of H+ 2 in the singlet ungerade channels computed with three distinct approaches. First, the fully numerically solvable two-dimensional approach developed at ÚTF MFF UK as a part of my master's thesis. Second, a vibrational frame transformation method based on the work of Chang and Fano [E. S. Chang and U. Fano, Phys. Rev. A 6, 173 (1972)] and then enhanced into a full energy-dependent form by Gao and Greene [H. Gao and C. H. Greene, J. Chem. Phys. 91, 3988 (1989)], [H. Gao and C. H. Greene, Phys. Rev. A 42, 6946 (1990)], fur- ther improved by our own revisions. Third, a two-dimensional R-matrix method based on matching exact 2D solutions from a small interaction region to asymptotic solutions in the non-interacting region. We thoroughly discuss the various advantages and caveats of these methods and, in the later chapters, present our work on employing them for the realistic recombination of HeH+ + e− . Furthermore, we attempt to extend the presented models to the description of the...
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Milne method and phase-amplitude method
Matějková, Markéta ; Soldán, Pavel (advisor) ; Čurík, Roman (referee)
Bound and quasi-bound states of one-dimensional systems play an important role in quantum physics. In this thesis we solve the Schrödinger equation numerically via the Milne method. We show the relation between the Schrödinger and the Milne equation. The quantum action and the quantum number function are defined. We find bound-state energies of chosen symmetrical and unsymmetrical potentials. Dependence of bound- state energies on the number of points and the step size is studied. We also analyze the influence of the choice of trial energies and the number of iterations. Then we modify the Milne equation and using the phase-amplitude method we illustrate the search of resonances on the example of a diatomic molecule. 1
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Radiative processes of small molecules
Šimsová, Martina ; Soldán, Pavel (advisor) ; Čurík, Roman (referee) ; Kalus, René (referee)
Four types of astrochemically relevant radiative processes are studied: bound-bound, bound-free, free-bound and free-free. The former two together determine radiative lifetimes, which are calculated for the HeLi+ molecular ion. Free-bound processes, also called radiative association, are studied on two systems: He in collisions with Li+ , and O in collision with C+. Collisions of He and Li+ are believed to have occurred during the recombination era of the Universe, while collisions of O with C+ are considered to be relevant in SN 1987A. Altogether, 17 radiative association cross sections and rate coefficients are calculated for radiative association, and the effect of a stimulated emission is also illustrated. A free-free process, also called radiative charge transfer, is studied in collisions of He with Li+.
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Quantization of dynamics of molecular rattleback.
Bačo, Zsolt ; Čížek, Martin (advisor) ; Čurík, Roman (referee)
Title: Quantization of dynamics of molecular rattleback Author: Zsolt Bačo Institute: Institute of Theoretical Physics Supervisor: doc. RNDr. Martin Čížek, Ph.D., Institute of Theoretical Physics Abstract: This thesis has a theoretical character and is dealing with the prob- lem of a molecular rattleback from the quantum perspective, based on knowledge from classical physics of the same system. It is a rotor which doesn't conserve a direction of rotation. The aim is a quantization of the system's energy, what is an objective for a matrix representation of hamiltonian and consecutive diago- nalization, for what a suitable mathematical apparatus is needed to be built. In this thesis, there are derivated equations in detail, which are needed for matrix elements of hamiltonian. The next aim is a study of spectrum of hamiltonian gained by numerical computes, specifically a convergence of approximate values and their statistics. Based on the spectrum's statistics, there is a discussion about the chaotic character of the system. The main contribution of this thesis is the method of computing energetic levels of rotating objects in potential. Keywords: quantum dynamics, energy spectrum, rotational movement, rattleback
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Two-dimensional model of dissociative recombination
Hvizdoš, Dávid ; Houfek, Karel (advisor) ; Čurík, Roman (referee)
The purpose of this thesis is to construct a numerically solvable quantum mechanical model describing the dynamics of the indirect mechanism of the dissociative recombination process of a molecular cation by electron impact. The model also describes vibrational excitation of a molecular cation by electron impact. The solution of this model is carried out by implementing a combination of finite elements, discrete variable representation and exterior complex scaling methods. This is then specifically applied to the dissociative recombination and vibrational excitation of H$_2^+$ by an incoming electron. The results can be used to test the accuracy of approximative methods and the programs expanded to cover the cases of other diatomics. Powered by TCPDF (www.tcpdf.org)
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