National Repository of Grey Literature 15 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Microscopic nuclear models for open-shell nuclei
Herko, Jakub ; Knapp, František (advisor) ; Kvasil, Jan (referee)
Title: Microscopic nuclear models for open-shell nuclei Author: Jakub Herko Institute: Institute of Particle and Nuclear Physics Supervisor: Mgr. František Knapp, Ph.D., Institute of Particle and Nuclear Physics Abstract: Since the nucleus is a quantum many-body system consisting of con- stituents whose mutual interaction is not satisfactorily known, it is necessary to use approximate methods when describing the nucleus. Basic approximate approaches in the microscopic theory of the nucleus are the Hartree-Fock the- ory, Tamm-Dancoff approximation and random phase approximation. They are described in the first chapter of this thesis. The main aim was to develop mi- croscopic models for open-shell nuclei with two valence particles or holes. They are described in the second chapter, which contains detailed derivations of the relevant formulae. These methods have been numerically implemented. The re- sults of the calculations of the nuclear spectra and the electromagnetic transition probabilities are presented in the third chapter. Keywords: Tamm-Dancoff approximation, random phase approximation, open- shell nuclei, nuclear spectra, electromagnetic transition probabilities ii
Giant monopole resonances in deformed nuclei
Božík, Daniel ; Kvasil, Jan (advisor) ; Mareš, Jiří (referee) ; Knapp, František (referee)
Title: Giant monopole resonances in deformed nuclei Author: Daniel Božík Department: Institute of particle and nuclear physics Supervisor: prof. RNDr. Jan Kvasil, DrSc., ÚČJF, MFF UK Abstract: The study of giant monopole resonances is important, because of its di- rect connection to the incompressibility of the nuclear matter, and its importance has risen with new experimental data obtained in recent years from the experi- ments TAMU and RCNP. The current work brings a study of the giant monopole resonances for chains of spherical (Pb, Sn, Zr) as well as deformed (Sm, Mo, Cd) isotopes. The calculations were carried out within the HFB + SRPA method, which was developed at MFF UK in cooperation with JINR Dubna and the University of Erlangen. We were as first able to confirm, from the microscopic theory, the appearance of a double-peak structure of GMR strength functions for deformed nuclei, and its connection with E0-E2 coupling. We showed the importance of using strength functions in the study of GMR. Keywords: HFB, SRPA, giant monopole resonances 1
Theoretical description of nuclear collective excitations
Repko, Anton ; Kvasil, Jan (advisor) ; Knapp, František (referee) ; Mareš, Jiří (referee)
Density functional theory is a preferred microscopic method for calculation of nuclear properties over the whole nuclear chart. Besides ground-state properties, which are calculated by Hartree-Fock theory, nuclear excitations can be described by means of Random Phase Approximation (RPA). The main objective of the present work is to give the RPA formalism for spherically symmetric nuclei, using the techniques of angular-momentum coupling. Various auxiliary topics, such as Hartree-Fock theory, Coulomb integral, center-of-mass corrections and pairing, are treated as well. RPA method is derived also for axially deformed nuclei. The derived formulae are then implemented in the computer code and utilized for calculation of some physical results. After thorough investigation of the precision aspects of the calculation, the following topics are treated as examples: toroidal nature of the low-energy (pygmy) part of the E1 resonance, giant resonances of various multipolarities in deformed nucleus 154Sm, and magnetic dipole (M1) transitions in deformed 50Cr. Powered by TCPDF (www.tcpdf.org)
Microscopic calculations of nuclear properties with realistic nucleon-nucleon interaction
Herko, Jakub ; Knapp, František (advisor) ; Kvasil, Jan (referee)
Title: Microscopic calculations of nuclear properties with realistic nucleon-nucleon interaction Author: Jakub Herko Department: Institute of Particle and Nuclear Physics Supervisor: Mgr. František Knapp, Ph.D., Institute of Particle and Nuclear Phy- sics Abstract: A significant problem of nuclear physics is the fact that the nucleus is quantum many-body system consisting of constituents whose mutual interac- tion is unknown. Therefore, it is necessary to use approximative methods when describing the nucleus. In the microscopic theory of the nucleus we often use the mean-field approximation, in which we consider non-interacting nucleons moving in external field. One approach to obtain an optimal mean-field is the Hartree- Fock method. The first part of this work is theoretical and describes methods of the microscopic theory of the nucleus, especially the Hartree-Fock method, with emphasis on formalism of the second quantization. The second part describes a practical implementation of the Hartree-Fock method in calculations of certain properties of the nuclei and calculations that go beyond this method and include the residual interaction using the perturbation theory. Keywords: Hartree-Fock method, nuclear binding energies, single-particle spectra, many-body perturbation theory
Photon strength functions in Gd isotopes studied from resonance neutron capture
Kroll, Jiří ; Krtička, Milan (advisor) ; Kvasil, Jan (referee) ; Granja, Carlos (referee)
Title: Photon strength functions in Gd isotopes studied from resonance neutron capture Author: RNDr. Jiří Kroll Department: Intitute of particle and nuclear physics Supervisor: doc. Mgr. Milan Krtička, Ph.D., Intitute of particle and nuclear physics Abstract: Photon strength functions have been studied for more than sixty years. A number of theoretical models was proposed to describe experimental data during that time. However, the correctness of these models is still very questionable and its verification is the subject of very intensive experimental and theoretical activity at present time. In this thesis the analysis of spectra of γ rays following the radiative capture of neutrons on isolated neutron resonances of 152,154−158 Gd nuclei is used to study photon strength functions. Experimental data were measured using segmented DANCE calorimeter that is installed at Los Alamos Neutron Scattering Center in New Mexico, USA. Experimental spectra are then compared with the outputs of Monte Carlo simulation of nuclear elec- tromagnetic decay, performed by DICEBOX code, that is based on the validity of the so-called Extreme Statistical Model. The response of the detector system to generated γ cascades was subsequently calculated using the Geant4 code. An analysis of the data clearly indicates that magnetic...
Analysis of dijet events in diffractive ep interactions with tagged leading proton at the H1 experiment
Polifka, Richard ; Kvasil, Jan (advisor)
Title: Analysis of dijet events in diffractive ep interactions with tagged leading proton at the H1 experiment Author: Richard Polifka Department: Institute of Particle and Nuclear Physics Supervisor: RNDr. Alice Valkárová, DrSc. Supervisor's e-mail address: avalkar@mail.desy.de Abstract: An inclusive dijet production in diffractive deep-inelastic scattering is measured. The diffractive selection is based on tagging of the leading proton in the Forward Proton Spectrometer. The statistics of events obtained during the HERA II running period (integrated luminosity of 156.7 pb−1 ) enables the measurement of jet final states with leading proton for the first time. The data cover the phase space of xIP < 0.1, |t| ≤ 1.0 GeV2 and 4 ≤ Q2 ≤ 110 GeV2 . The dijet data are compared with the next to leading order predictions of the quantum chromodynamics (QCD). The phase space of diffractive dijets is in this analysis by factor of 3 in xIP larger than in previous measurements. The QCD predictions based on the DGLAP parton evolution describe the measured data well even in a non-DGLAP enriched phase space where one on the jets goes into the region close to the direction of the outgoing proton. The measured single-differential cross sections are compared to several Monte Carlo models with different treatment of...
Gigantické rezonance v atomových jádrech
Repko, Anton ; Kvasil, Jan (advisor) ; Knapp, František (referee)
Skyrme functional is commonly used for the description of ground-state and dynamical properties of atomic nuclei. To describe the dynamical properties in the microscopic self-consistent way, we employed Separable Random Phase Approximation (SRPA) based on Skyrme functional. This work describes theory of Skyrme Hartree-Fock and SRPA and presents numerical calculation of E1 and M1 giant resonances in spherical nuclei Ca-40 - Fe-56. There is some evidence for non-zero ground-state deformation of the nucleus Fe-56, so it is treated also with such assumption. The results obtained for various parametrizations are compared to the experimental data.
Jaderné kolektivní stupně volnosti a Skyrme funkcionál
Božík, Daniel ; Kvasil, Jan (advisor) ; Cejnar, Pavel (referee)
Title: Energy functional theories in nuclear physics Author: Daniel Božík Department: Institute of Particle and Nuclear Physics of Charles University Supervisor: prof. RNDr. Jan Kvasil, DrSc. Supervisor's e-mail address: kvasil@ipnp.troja.mff.cuni.cz Abstract: In the present work we study the giant resonances of the chain of even-even samarium nuclei 144−154 Sm. The numerical calculations are provided by a chain of numer- ical codes. Mean field is calculated by the HFB method for the Skyrme density functional and the residual interaction is included by the separable RPA method, which was devel- oped at IPNP MFF UK and JINR Dubna. The studied resonances are E1, E2 and M1. A special interest is paid to pygmy and scissor modes. The dependence of the pygmy modes on the deformation of nuclei is studied. The linear dependence of the integral scissor mode strength on the square of the nuclear deformation is verified within our microscopic model. Keywords: Skyrme functional, separable RPA, electric and magnetic giant resonances
Photon strength functuins in 177Lu from two-step gamma cascade measurement
Valenta, Stanislav ; Krtička, Milan (advisor) ; Kvasil, Jan (referee)
The subject of the study made in this work are photon strength functions. Many models, both based on theoretical as well as phenomenological approaches, were proposed for these quantities, describing the gamma decay of the nucleus, during last 50 year. However, the correctness of these models is still questionable and its verification is the subject of intensive experimental and theoretical activity at the present time. The results of the analysis of measurements of the two-step cascades following thermal neutron capture on the 176Lu nucleus are compared with the outputs of the Monte Carlo simulations based on the validity of the so-called Extreme Statistical Model. Comparison of experimental data with outcomes of simulations thus becomes the basic tool for studying correctness of theoretical models. The experiment analyzed in the present work provides information mainly about E1 and M1 photon strength functions, especially about the so-called scissors resonance.

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