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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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Studium biologicky relevantních systémů v elektronicky excitovaných stavech
Zámečníková, Martina ; Soldán, Pavel (advisor) ; Bludský, Ota (referee) ; Nachtigallová, Dana (referee)
Very short lifetimes of excited states of isolated bases in nucleic acids, on the picosec- ond order, are believed to contribute to photostability of the genetic code. When embedded in DNA this behavior becomes more complex, mainly due to their inter- actions via stacking and hydrogen bonding. The DNA photophysiscs is not fully understood yet. It depends e.g. on the conformation and the character of excited states. The studies on smaller systems can help to improve the understanding of these phenomena. The aim of this work was to examine the dynamics of the excited states of the n → π∗ character of the complex of N-methylformamide dimer and two waters. The study was performed using non-adiabatic dynamics simulations with on-the-fly Surface Hopping algorithm based on the potential energy surfaces and non-adiabatic couplings obtained with multi-reference approach. The results show that after the vertical excitation into delocalized S2 state the system relaxes into S1 state within several tens femtoseconds. For majority of the population, the charac- ter of the state then oscillates between localized and delocalized during the whole course of the dynamics. Comparison with calculations with the waters removed in- dicates that the delocalization is caused by waters serving as a bridge between the two chromophores. 1
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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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Radiative processes of small molecules
Šimsová, Martina ; Soldán, Pavel (advisor)
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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Coupled clusters tailored by matrix product state wave functions
Antalík, Andrej ; Pittner, Jiří (advisor) ; Noga, Jozef (referee) ; Soldán, Pavel (referee)
The central problem in the modern electronic structure theory is the calculation of cor- relation energy, possibly by an approach that would account for both static and dynamic correlation in an efficient, balanced and accurate way. In this thesis, I present a collection of methods that combine the effective treatment of dynamic correlation by the coupled cluster theory with density matrix renormalization group, a well-established technique for calculations of strongly correlated systems. The connection between them is achieved via the tailored coupled clusters (TCC) ansatz, which conveniently does not impose any ad- ditional computational costs. After the successful initial assessment, we developed more efficient implementations of these methods by employing the local approaches based on pair natural orbitals. This way, we extended the range of possible applications to larger systems with thousands of basis functions. To assess the accuracy of TCC as well as its local counterparts, we performed a variety of benchmark calculations ranging from small, yet challenging systems such as the nitrogen molecule or tetramethyleneethane diradical, to larger molecules like oxo-Mn(Salen) or Fe(II)-porphyrin model. 1
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Potential energy surface of the HeNO+complex
Vranková, Veronika ; Soldán, Pavel (advisor) ; Bludský, Ota (referee)
V tejto práci sme sa zaoberali konštrukciou plochy potenciálnej energie molekulárneho komplexu HeNO + z poskytnutých ab initio dát. Ako prvé sme odvodili kvali- tatívne korektný výraz pre interakčný Hamiltonián komplexu HeNO + pre ve©ké intermolekulárne vzdialenosti. Rozhodli sme sa pracova' v multipólovej aprox- imácii, ktorú je možné použi' práve pri ve©kých intermolekulárnych vzdialenos- tiach. Pre multipólový rozvoj sme použili formuláciu kartézskych tenzorov. Takýto interakčný Hamiltonián bol následne použitý ako porucha systému v poruchovej teórii intermolekulárnych síl, z ktorej sme odvodlili výraz pre elektro- statickú, indukčnú a disperznú energiu. Tento záver bol potrebný pre konštruk- ciu korektného reprodukčného jadra pre 1D RKHS interpoláčnú a extrapolačnú procedúru, ktorú sme skombinovali s Gaussovou-Legendrovou kvadratúrou. Napísali sme program v jazyku Fortran90, ktorý prislúcha našim teoretickým výsledkom a ktorého výstupom sú hodnoty interakčného potenciálu na vopred zvolených súradniciach. Taktiež sme určili globálne minimum a sedlové body plochy po- tenciálnej energie HeNO + komplexu. 1
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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)
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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