Microscopic theory of nuclear-structure effects in atomic systems

In this thesis, nuclear-structure effects in atomic systems are investigated from the microscopic point of view. To this end, a detailed description of nuclear dynamics is incorporated into calculations of the finite-nuclear-size and nuclear-polarization corrections to atomic energy levels and the bound-electron g factor. Hydrogen-like highly charged ions as well as muonic atoms are considered. Nuclear ground-state charge distributions are obtained within the Hartree-Fock method, while complete nuclear excitation spectra are computed by means of the random-phase approximation. The interaction between nucleons is modelled by the effective Skyrme force. The effects of nuclear excitations on atomic properties are described in a field-theoretical framework, where the full Dirac spectrum of a bound electron or muon is taken into account with the help of finite basis-set methods. Special attention is given to analyzing the nuclear model dependence, and the uncertainties of the calculations are estimated. In addition, the suppression of nuclear-structure effects in various weighted differences is discussed. Finally, the developed methods and computational codes are applied to the long-standing problem of the fine-structure anomalies in heavy muonic atoms

Testing standard-model extensions with isotope shifts in few-electron ions

When collecting spectroscopic data on at least four isotopes, nonlinearitiesin the King plot are a possible sign of Physics beyond the Standard Model. Inthis work, an improved approach to the search for hypothetical new interactionswith isotope shift spectroscopy of few-electron ions is presented. Very carefulaccount is taken of the small nuclear corrections to the energy levels and thegyromagnetic factors, which cause deviations from King linearity within theStandard Model and are hence a possible source of confounds. In this newapproach, the experimental King nonlinearity is not compared to the vanishingprediction of the Standard Model at the leading order, but to the calculatedfull Standard Model contribution to King nonlinearity. This makes searching forbeyond-the-Standard-Model physics with King linearity analysis possible in avery-high-precision experimental regime, avoiding confounds. The bounds whichcan be set on beyond-the-Standard-Model parameters remain limited by theuncertainties on the small Standard Model nuclear corrections which cause Kingnonlinearity. Direct comparison between theory and experiment on a single pairof isotopes is advocated as a more suitable approach for few-electron ions.<br

Evidence Against Nuclear Polarization as Source of Fine-Structure Anomalies in Muonic Atoms

A long-standing problem of fine-structure anomalies in muonic atoms is revisited by considering the $\Delta 2p$ splitting in muonic $^{90}\mathrm{Zr}$, $^{120}\mathrm{Sn}$ and $^{208}\mathrm{Pb}$ and the $\Delta 3p$ splitting in muonic $^{208}\mathrm{Pb}$. State-of-the-art techniques from both nuclear and atomic physics are brought together in order to perform the most comprehensive to date calculations of nuclear-polarization energy shifts. Barring the more subtle case of muonic $^{208}\mathrm{Pb}$, the results suggest that the dominant calculation uncertainty is much smaller than the persisting discrepancies between theory and experiment. We conclude that the resolution to the anomalies is likely to be rooted in refined QED corrections or even some other previously unaccounted-for contributions

Thin structure of steel St52, 3N and possible reasons of defect of large-capacity billets AT "YURMASH"

Electron-microscopic and x-ray investigations of structurally-phase and intense-deformed condition of material made of defective and conditional forged billet at «Yurmash» have been carried out. It is ascertained that in steel made from the defective forged piece the fraction of perlite is 1,5...2 times higher and lamellar perlite prevails. Local long-range tensions in both conditions of material are commensurable with fluidity limit. The content of sulfides is considerably higher in the steel made from the defective billet. They are located in the body of ferrite grains and along the interfaces. In the material made from the conditional forging they are located only inside of grains. The scalar density of dislocations in ferrite grains and in ferrite layers of perlite of the defected billet is one and a half time higher than in conditional metal. All the totality of the listed above circumstances allows stating that the main cause of cracking of large-capacity billets made of steel St52, 3N is not a full conformity of the chemical compound to branded requirements

Optimizing Technological Parameters of the Reduction Processes in Treating Steels in a Ladle Furnace

This work reports the possible development of reduction processes when treating the molten metal and slag using a ladle furnace under conditions of intensive stirring with an inert gas. The industrial data have been received, confirming the possibility of decreasing the concentration of ferrous and manganese oxides in the slag and stabilizing the contents of manganese and silicon in the metal

Influence of Cooling Rate in High-Temperature Area on Hardening of Deposited High-Cutting Chrome-Tungsten Metal

The authors study the influence of cooling rate in high-temperature area for thermal cycle of high-cutting chrome-tungsten metal weld deposit on the processes of carbide phase merging and austenite grain growth for the purpose of providing high hardness of deposited metal (HRC 64-66)

Development and Study of Hard-Facing Materials on the Base of Heat-Resisting High-Hardness Steels for Plasma-Jet Hard- Facing in Shielding-Doping Nitrogen Atmosphere

The authors develop hard-facing materials on the base of heat-resisting highhardness steels for plasma-jet hard-facing in nitrogen atmosphere for manufacturing parts of mining and metallurgic equipment which significantly simplify the production process and effect a saving when producing bimetallic parts and tools

Developing and Studying the Methods of Hard-Facing with Heat-Resisting High-Hardness Steels

The authors develop the methods of hard-facing of mining-metallurgic equipment parts with heat-resisting high-hardness steels on the base of plasma-jet hard-facing in the shielding-alloying nitrogen atmosphere

Distribution of Liquid Flow Rates in the Process of Bubbling with Gas Through Gas-Permeable Inserts

The authors studied the distribution of the vertical components of the rate in the ascending gas-liquid flow when blowing through the bottom nozzle at two levels under three modes of neutral gas supply. It was estimated that under the intensities of gas (nitrogen) of 2 and 4 L/min-t the type of rates distribution in both cross-sections does not differ from the generally accepted one and practically does not depend upon the intensity of gas supply