Thin target L-Shell x-ray production cross sections for protons incident on ₆₂Sm and ₇₀Yb in the energy range of 0.3 to 2.4 MeV/amu, alpha particles incident on ₆₂Sm, ₇₀Yb, and ₈₂Pb in the energy range of 0.15 to 4.8 MeV/amu, and lithium ions incident on ₅₈Ce, ₆₀Nd, ₆₂Sm, ₆₆Dy, ₆₇Ho, ₇₀Yb, and ₈₂Pb in the energy range of 0.8 to 4.4 MeV/amu have been measured. The cross section data have been compared to the planewave Born approximation (PWBA) and the PWBA modified to include binding energy and Coulomb deflection effects. The Lα₁,₂ x-ray production cross sections are best represented by the PWBA modified to include both the binding energy and Coulomb deflection effects (PWBA-BC) over the entire incident ion, incident energy, and target ranges studied. However, the Lγ₁ and Lγ₂,₃,₍₆₎ x-ray production cross sections are best represented by the PWBA except at the lower ion energies, where both the PWBA and PWBA-BC are in disagreement with the data. The comparison of Lα₁,₂/Lγ₂,₃,₍₆₎ ratios to theory reveals that the PWBA-BC does not predict the inflection point substantiated by the data, and the agreement between the data and the PWBA-BC becomes worse as the atomic number of the incident ion increases. Comparison of the PWBA modified to include binding energy effects CPWBA-B) and the PWBA modified to include Coulomb deflection effects (PWBA-C) to the Lα₁,₂, Lγ₁, and the Lγ₂,₃ cross sections for protons, alpha particles, and lithium ions incident on ₇₀Yb indicates that the PWBA-C overestimates the magnitude of the data but does describe the shape of the L₁-associated cross section while the PWBA-B underestimates the magnitude of the data but fails to predict the proper shape of the L₁-associated data. In order to evaluate the ability of the PWBA and the presently accepted modifications to the PWBA to fit the experimental data, future experimentation should be conducted in the energy range that includes the point where the ratio of the incident ion velocity to the L-Shell electron velocity is equal to 0.19 (i.e., V₁/Vₗ = 0.19). This is where the L₁-associated cross sections begin to exhibit the shouldered structure and the cross section ratios L₃/L₁ and L₂/L₁ have inflection points.

>Magister Scientiae - MSc / This thesis aims at developing a sorting code for Coulomb excitation studies at iThemba LABS. In Coulomb excitation reactions, the inelastic scattering of the projectile transfers energy to the partner nucleus (and vice-versa) through a time-dependent electromagnetic field. At energies well below the Coulomb barrier, the particles interact solely through the well known electromagnetic interaction, thereby excluding nuclear excitations from the process . The data can therefore be analyzed using a semiclassical approximation. The sorting code was used to process and analyze data acquired from the Coulomb excitation of 20Ne beams at 73 and 96 MeV, onto a 194Pt target. The detection of gamma rays was done using the AFRODITE HPGe clover detector array, which consists of nine clover detectors, in coincidence with the 20Ne particles detected with an S3 double-sided silicon detector. The new sorting code includes Doppler-correction effects, charge-sharing, energy and time conditions, kinematics and stopping powers, among others, and can be used for any particle-γ coincidence measurements at iThemba LABS. Results from other Coulomb excitation measurements at iThemba LABS will also be presented.

Philosophiae Doctor - PhD / The Coulomb excitation of 66Ge has been performed for the rst time using \safe" bombarding energies at the HIE-ISOLDE facility at CERN in July 2017. A particle- coincidence experiment using the MINIBALL array and double-sided silicon detectors has allowed the determination of transitional and diagonal matrix elements in 66Ge, yielding new measurements of the reduced transition probability connecting the ground state, 0+1 , and the rst excited state, 2+1 , or B(E2; 2+1 ! 0+1 ) value, and the spectroscopic quadrupole moment of the 2+1 state, QS (2+1 ). A relatively large B(E2) = 29:4(30) W.u. has been extracted using beam-gated data at forward angles { less sensitive to secondorder e ects { as compared with the adopted value of 16:9(7) W.u., but in closer agreement with modern large-scale shell-model calculations using a variety of e ective interactions and beyond-mean eld calculations presented in the current work. / 2022

>Magister Scientiae - MSc / In this work we have determined the spectroscopic or static quadrupole moment of the rst excited state (QS (2+1) lying at 2230.6 keV in 32S using the reorientation e ect. The Coulomb-excitation experiment at safe bombarding energies was performed at iThemba LABS's AFRODITE vault, where 32S beams at 120.3 MeV were bombarded onto a 194Pt target of 1 mg/cm2 thickness. The beam energy has been chosen such that the separation between nuclear surfaces is greater than 6.5 fm at all scattering angles, in order to avoid nuclear interactions. A double-sided CD-type S3 silicon detector, with 24 rings and 32 sectors, has been placed upstream (at backward angles) to detect the scattered particles. Gamma rays have been detected with the AFRODITE clover array. This particle-gamma coincidence experiment allows for an angular distribution and Doppler correction of the gamma rays emitted at 9% the speed of light. The cross sections (or gamma-ray integrated yields) measured as a function of scattering angle at backward angles are sensitive to second-order perturbation e ects in Coulomb excitation, i.e., diagonal matrix elements which are directly related to the spectroscopic quadrupole moment. The gamma-ray integrated yields obtained from this experiment are compared with the GOSIA simulations, yielding a new measurement of QS (2+1) = 􀀀0:10 0:7 eb, which corresponds to a prolate shape in the intrinsic frame of the nucleus. The uncertainty of this measurement is limited by statistics. This result agrees with previous measurements and con rms the zig zag of shapes at the end of the sd shell when approaching the doubly-magic nucleus 40Ca. Nonetheless, the mystery continues as a prolate shape for the rst 2+ disagrees with modern theoretical mean- eld calculations and the pairing coupling model.

The electron-electron interaction is the origin of many interesting phenomena in condensed matter. These phenomena post challenges to theoretical physics and can lead to important future applications. Transition metal dichalcogenide heterostructures provide excellent platforms to study these phenomena because of the two-dimensional nature, large effective mass and tunable bandwidth with moiré potential. As electron bands become narrower such that the Coulomb interaction energy becomes comparable to the bandwidth, interactions can drive new quantum phases. This dissertation describes the realization of this platform and probing of correlated phenomena with low- temperature transport measurements. As the first step, the electrical contact problem of few-layer transition metal dichalcogenides, which prohibits low-temperature transport measurements, needs to be solved. Two different contact schemes have been used to attack this problem. For p-type transition metal dichalcogenide, prepatterned platinum is used to bottom contact transition metal dichalcogenides. This method prevents channel from deterioration due to electron beam evaporation and the high workfunction platinum can place the Fermi level underneath the material valence band. Alternatively, for n-type transition metal dichalcogenides, a single layer of boron nitride is put on transition metal dichalcogenide before cobalt evaporation. This way, the boron nitride layer protects the transition metal dichalcogenide from the process of evaporation and can decrease the work function of cobalt thus putting Fermi level above the conduction band. With these contact methods, Ohmic contacts can be achieved at cryogenic temperature and probing the transition metal dichalcogenide heterostructures with transport measurements become accessible. Then, the magnetotransport properties of monolayer molybdenum disulphide and bilayer tungsten diselenide encapsulated with boron nitride with graphite dual-gate were measured. There are three unique features underlie this two dimensional electron gas system. First, the system is strong correlated. The Landau level spectrum reveals strong correlated signatures, such as enhanced spin-orbit coupling splitting and enhanced effective g-factor. Second, the longitudinal resistance/conductance at half-filling of Landau levels are found to depend on the spin orientation. The minority spin Landau level become totally localized at higher magnetic field. Third, in bilayer device the two layers are weak coupled and can be independently controlled by two gates. All this features establish transition metal dichalcogenide a unique platform for studying correlated physics. Finally, to achieve higher level of correlation, two layers of tungsten diselenide are stacked together with a small twist angle. With the help of moiré potential and layer hybridization, the bandwidth can be continuously tuned by the twist angle. In the range of 3 degree to 5.1degree, with moderate correlation strength, correlated insulating states are shown at half-filled flatband and are highly tunable with vertical electric field.

Effective Field Theory (EFT) provides a systematic framework to study nuclear structure at low energy. The present work uses EFT to study the Coulomb effects in protonproton scattering. The Coulomb phase shift for elastic scattering is calculated. The calculation done here are on a lattice with periodic boundary conditions, and has a hard spherical wall imposed on it. The scattering inside the sphere produces spherical standing waves, the properties of which are exploited to calculate the phase shift and then compared with known theoretical calculations.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24406号 / 理博第4905号 / 新制||理||1701(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 中家 剛, 准教授 WENDELL Roger, 教授 永江 知文 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

In this thesis, we studied the self-assembly of nanoparticles at liquid metal-water interfaces and oil-water interfaces. We demonstrated a simple approach to form nanostructured electronic devices by self-assembly of nanoparticles at liquid metal surfaces. In this approach, two liquid-metal droplets, which were coated with a monolayer of ligand-stabilized nanoparticles, were brought into contact. They did not coalesce but instead remained separated by the nanoparticles assembled at the interface. Devices formed by this method showed electron transport between droplets that was characteristic of the Coulomb blockade, where current was suppressed below a tunable threshold voltage because of the energy of charging individual nanoparticles. Further studies of this approach demonstrated the potential of interfacial assembly in fabricating microscopic electronic devices over a large area in a cost-effective and time-efficient fashion. Micrometer-scale Ga droplets coated with nanoparticles were fabricated using ultrasonication and then deposited on patterned substrates to form microscopic devices. I-V measurements showed Coulomb blockade effect in the devices containing more than one nanoparticle junction. The measured threshold voltages increased with number of junctions as expected for devices arranged in series. We also studied experimentally the energy of adsorption of nanoparticles and microparticles at the oil-water and Ga-water interfaces by monitoring the decrease of interfacial tension as the particles bind. For citrate-stabilized gold nanoparticles assembling on a droplet of octafluoropentyl acrylate, we found adsorption energy =-5.1 kBT for particle radius R = 2.5 nm, and adsorption energy scales R^2 for larger sizes. Gold nanoparticles with (1-mercaptoundec-11-yl) tetra(ethylene glycol) ligand had a much larger binding energy (-60.4 kBT) and an energy barrier against adsorption. For polystyrene spheres with R = 1.05 micrometer, we found adsorption energy =-0.9*10^6 kBT. We also found that the binding energy depended on the composition of the oil phase and could be tuned by the salt concentration of the nanoparticle suspension. At Ga-water interfaces, we found that adsorption energy of Au-cit and Au-TEG nanoparticles were much larger. We have also studied desorption of polystyrene microparticles from oil-water interfaces by changing experimental conditions, including addition of nanoparticles, cross-linking ligand molecules or in response to chemical interactions between the particles and the oil. We found that microparticles can desorb even though the adsorption energy is large. We also found that the desorbed particle formed a surprising `tail'-like structure.

<p> A variety of experiments has been performed in order to establish and identify the states in 191Ir and 193Ir. From radioactive decay, the energies and intensities of the gamma rays and internal conversion electrons have been measured with high precision using Ge(Li) detectors and the Chalk River π√2 spectrometer. A series of gamma-gamma coincidence experiments were performed using Ge(Li) detectors. The gamma rays following Coulomb excitation of 191Ir and 193Ir were also measured with Ge(Li) detectors. In addition, (3He,d) and (α,t) transfer reactions were performed and the reaction products analyzed by means of an Enge split-pole spectrograph. From these data, the energies, spins, parities and spectroscopic factors for the states in 191Ir and 193Ir have been established and interpreted in terms of the Nilsson model with band mixing.</p> / Thesis / Doctor of Philosophy (PhD)

<p> We study the Coulomb effect on the proton-proton low-energy scattering parameters when all other effects are represented by a separable potential.</p> <p> For this purpose, we present a formulation for the scattering of two particles via a separable potential. We treat the same problem when any potential, particularly a Coulomb potential or a separable potential, is added to the separable potential. The properties of scattering from a separable potential plus a (local or non-local) potential lead us to the possibility of obtaining a one term separable potential equivalent to a two term separable potential, and a model for the nuclear potential as a sum of a separable potential and a non-separable potential.</p> <p> We determine, to the first order in Me^2/β where β^-1 is the range of the separable potential, the parameters for Yamaguchi's and Naqvi's separable potentials from proton-proton scattering data. We use these parameters to calculate the low-energy proton-proton scattering parameters when the Coulomb interaction is removed. Our results show that the shape dependence of these parameters are somewhat larger than obtained by Heller et al in their investigation on local potentials. Implications of our results concerning the charge symmetry and charge independence of the nuclear forces are discussed.</p> / Thesis / Master of Science (MSc)