Classically a nanowire with a length larger than its circumference is expected to be unstable due to Rayleigh instability that appears in specimens with large aspect ratio. In contrast we present... Show moreClassically a nanowire with a length larger than its circumference is expected to be unstable due to Rayleigh instability that appears in specimens with large aspect ratio. In contrast we present experimental evidence that metallic nanowires with thicknesses ranging from one atom to hundreds of atoms present two series of exceptionally stable diameters, well determined and reproducible. The two series of stable diameters can be described in terms of shell closure effects. For low diameters the stability is given by the confinement of the electronic orbits in the nanowire cross-section, which is an electronic shell effect. Thicker nanowires are stable for densely packed structures, related to minima in the surface energy, which we refer to as atomic shell effect. A significant part of this thesis is dedicated to the study of shell effects for different types of metals: the monovalent noble metals, and multivalent Al and Mg. Additionally we investigate the stability from a mechanical point of view by measuring the stiffness of atomic contacts. The last chapter is dedicated to electrochemical methods of nanowire fabrication and we explore possible ways of enhancing the nanowire stability. Show less
The initial goal of this thesis was to demonstrate chaos in an open two-mirror resonator. We have designed a bifocal mirror that forms a resonator with an unstable inner and a stable outer part. To... Show moreThe initial goal of this thesis was to demonstrate chaos in an open two-mirror resonator. We have designed a bifocal mirror that forms a resonator with an unstable inner and a stable outer part. To be able to distinguish phenomena unique for configuration from phenomena also present in conventional resonators, i.e., roughness-induced scattering and aberrations, the performance of a conventional stable resonator is investigated first. Roughness-induced scattering turns out to affect the cavity finesse as well as the average power throughput and produces mode coupling close to frequency-degenerate points. We demonstrate, furthermore, a method to accurately determine aberrations by measuring the Gouy phase of subsequent higher-order modes around frequency-degeneracy. The bifocal mirror is not fabricated by traditional grinding and polishing, but by diamond-machining. The eigenmodes of a resonator with one diamond-machined bifocal mirror turn out to be Laguerre-Gaussian. We demonstrate furthermore, the coupling of two resonators based on transmission spectra and patterns, and report on the ability of the configuration to fulfill the basic requirements to obtain chaos. Show less
The main theme of this thesis is the catalytic oxidation of CO, which we have investigated on several model catalyst surfaces at atmospheric pressures and elevated temperatures with the combination... Show moreThe main theme of this thesis is the catalytic oxidation of CO, which we have investigated on several model catalyst surfaces at atmospheric pressures and elevated temperatures with the combination of Scanning Tunneling Microscopy and Mass Spectrometry.The study of CO oxidation on low-index and vicinal palladium surfaces has shown that when exposed to ambient pressures of oxygen at elevated temperature, these surfaces oxidize irrespective of their orientation. In this pressure regime the oxides were shown to have a higher reactivity than the metallic surfaces.In a certain window of partial pressure combinations of O2 and CO reaction rate oscillations were observed on Pd(100) and on its vicinal surface Pd(1.1.17). ). CO adsorption on Pt(111) was found to lead to the formation of a regular overlayer structure, identified as (√19 x √19) R23.4°-13CO. The stability of this structure under different reaction conditions was discussed. These results were further used to illustrate the importance of temperature in a catalytic system.Spectacularly high conversion rates could be achieved during CO oxidation at atmospheric pressure on metallic Pt(100) surface. Show less
One of the most intriguing concepts of quantum mechanics is quantum entanglement. Two physical systems are said to be entangled with respect to a certain variable, if their individual outcomes of... Show moreOne of the most intriguing concepts of quantum mechanics is quantum entanglement. Two physical systems are said to be entangled with respect to a certain variable, if their individual outcomes of the variable are undetermined before measurement, but strictly correlated. Measurement of the variable for only one system immediately determines the outcome for the other system, irrespective of the distance between the two systems. It is this strong correlation that provides a basis for perspective, powerful applications like quantum cryptography and quantum computation. The most studied entangled systems, often called EPR systems (after the pioneers Einstein, Podolsky and Rosen), are pairs of light particles or photon pairs. These photon pairs, usually generated via the optical process of a spontaneous parametric down-conversion, are, in principal, simultaneously entangled in three variables, being polarization (polarization entanglement), energy or time (time entanglement), and momentum or transverse space (spatial entanglement). The contents of this thesis cover new insights in the polarization and spatial entanglement of photons. We have investigated both the entanglement quality and the yield of entangled photons for different experimental geometries that are associated with the production and detection of the photons. Show less
This work entitled as "Atomic-scale friction: thermal effects and capillary condensation" is a study on the fundamental aspects of the origin of friction from the atomic-scale. We study two... Show moreThis work entitled as "Atomic-scale friction: thermal effects and capillary condensation" is a study on the fundamental aspects of the origin of friction from the atomic-scale. We study two realistic aspects of atomic-scale friction, namely the effect of temperature and the effect of relative humidity of the environment. To study this, we used a home-built friction force microscope (FFM) where a sharp tungsten tip was scanning over a graphite surface. We find that thermal activation of the tip reduces friction significantly, whereas the water condensing between the tip and the surface as a result of capillary condensation increases atomic-scale friction. Water condensing between the tip and the surface forms ice at room temperature and the tip writes a line of ice on the surface. Therefore, we find that water acts like a glue rater than a lubricant in atomic-scale friction. Show less
This thesis is focused on the study of phase transitions and universal critical phenomena of spin lattice models. New Monte Carlo algorithms were developed that enable the investigation of such... Show moreThis thesis is focused on the study of phase transitions and universal critical phenomena of spin lattice models. New Monte Carlo algorithms were developed that enable the investigation of such models. A new level of accuracy is achieved in the determination of the universal parameters of the most common type of critical transition in nature, the Ising transition in three dimensions. The work took place at the Lorentz Institute for theoretical physics, under the guidance of Prof. Dr. H. W. J. Bl\"ote. The main results of this thesis are in the field of theoretical and computational physics. Show less
