This thesis reports on the development of a novel mass spectrometer combining image charge detection with surface induced dissociation for real-time analysis of intact viruses. Protonated viruses produced using electrospray are accelerated and subsequently impact on a solid surface. Capsid peptides released during the impact are analyzed using time-of-flight mass spectrometry. Image charge detection is used to measure the mass and charge states of structurally intact, electrosprayed viruses prior to impact. Since virus capsids are composed of loosely-bound proteins, collision of viruses with surfaces at moderate impact energies could release intact proteins. The masses and numbers of different protein types combined with the mass of the intact virus represent a unique signature useful for accurate, real-time virus identification. The progress of instrumentation developed thus far is reported. Techniques were developed for electrospraying intact viruses, including electrospray capillaries with small tips and methods for achieving complete desolvation. Significant reduction of low-frequency and other noise was achieved in the image charge detector as well as determination of accurate methods for mass and charge measurement. Improved focusing and transmission efficiency was achieved via an aerodynamic lens. Suitable surfaces were also obtained including conductive diamond and fluorinated self-assembled monolayer (SAM) surfaces.

The work of this thesis focuses on the interaction of high Rydberg states of hydrogen molecules and atoms with various doped Si semiconductor surfaces with the results compared with those obtained with an atomically flat gold surface. The major part of the thesis was carried out using para-H₂ molecular Rydberg states with principal quantum number n = 17 - 21 and core rotational quantum number N⁺ = 2. Subsequently, this study was continued using H atomic Rydberg states with principal quantum number n = 29 - 34. The high Rydberg states have been produced using two-step laser excitation. For close Rydberg surface separation (< 6 n² a.u.), the Rydberg states may be ionized due to an attractive surface potential experienced by the Rydberg electron, and the remaining ion core may be detected by applying an external electric field. An efficient ion detectability method is introduced to compare the many surface ionization profiles quantitatively. The p-type doped Si surfaces enhance the detected ion-signal more than the n-type doped Si surfaces due to the presence of widely distributed positive dopant charge fields in the p-type doped Si surfaces. As the dopant density increases, the area sampled by the resultant ions becomes effectively more neutral, and the decay rate of the potential from the surface dopant charge with distance from the surface becomes more rapid. Therefore, the minimum ionization distance is also reduced with increasing dopant density. It is found that the detected ion-signal decreases with increasing dopant density of both p- and n- type doped Si surfaces. The higher-n Rydberg states have shown higher ion detectability than that of lower-n Rydberg states and this variation also becomes smaller when increasing the dopant density. Experiments involving H2 Rydberg molecules incident on various doped Si surfaces in the presence of a Stark field at the point of excitation are also presented here. The surface ionization profiles produced via both electron and ion detection schemes are measured by changing the Stark polarization. Positive surface dopant charges oppose production of backscattered electrons and negative surface dopant charges enhance the electron-signal. For the electron detection scheme, lightly doped n-type Si surfaces show higher detectability but in the case of p-type Si surfaces the more heavily doped Si surfaces give a higher detected signal. This different behaviour of the detected ion or electron signal implies a different production mechanism. Theoretical trajectory simulations were also carried out based on a new 2D surface potential model. The results qualitatively agree with the experimental results and explain the changes of the surface ionization profiles between the various dopant types and dopant densities of the Si surfaces.

Image-charge detection is emerging as an important tool to analyze heavy and heterogeneous samples because of its unique advantages in measuring highly charged microparticles. Conventional image-charge detection instruments include at least three fundamental components: an ionization source, an aerodynamic particle delivery system, and an image-charge detector. Here I report research efforts that investigated the mechanisms of image-charge detection and proposed some instrumental developments of these components to suit specific research purposes. In Chapter 2, I report an investigation of the electrospray ionization (ESI) mechanism based on an observation that a certain portion of charged particles generated with an ESI source carried charges opposite to the needle which is biased with a high voltage. Both biological and non-biological samples were used to shed a light on the complex process of droplet evolution in ESI. In Chapter 3, I present two novel designs of printed circuit board (PCB) based image-charge detectors. With these detectors, not only the charge and velocity of each microparticle were investigated, but also the two dimensional trajectories, with applications in aerosolized particle beam diagnostics. Chapter 4 shows several designs of the microparticle delivering system aiming to achieve a faster acceleration of sample microparticles. Finally, Chapter 5 presents some thoughts on future directions for these projects.

Image charge detection is a non-perturbative pre-detection approach for deterministic ion implantation. Using low energy ion bunches as a model system for highly charged single ions, we experimentally studied the error and detection rates of an image charge detector setup. The probability density functions of the signal amplitudes in the Fourier spectrum can be modelled with a generalised gamma distribution to predict error and detection rates. It is shown that the false positive error rate can be minimised at the cost of detection rate, but this does not impair the fidelity of a deterministic implantation process. Independent of the ion species, at a signal to-noise ratio of 2, a false positive error rate of 0.1% is achieved, while the detection rate is about 22%

Charge detection mass spectrometry (CDMS) is a single particle technique capable of simultaneously measuring charge and mass-to-charge ratios for individual ions or particles. The linear array CDMS design theoretically has no upper mass limit and is therefore a choice method for the analysis of high mass and heterogeneous samples, such as dust microparticles in the Martian atmosphere. This dissertation describes the development of a novel charge detection mass spectrometer made of printed circuit boards (PCB) for the analysis of dust microparticles in the Martian atmosphere. Development of this device has required investigations in analysis methods and the engineering design of both the PCB device and the vacuum chamber system used in laboratory experiments. Accurate velocity analysis is crucial in determining correct particle mass in linear array CDMS. By combining the Shockley-Ramo theorem–which allows for the calculation of instantaneous image current for a system of electrodes when a point charge passes them–and SIMION ion optics simulations effective electrode length can be determined for any given charge detector geometry and aid in charge detector engineering and design process. Applying these simulation results to experimental data yields velocity agreement for a PCB charge detector within 0.44% RSD. The novel PCB CDMS device was demonstrated for the analysis of multiple types of microparticles of varying size and charge similar to that expected of atmospheric Mars dust. This device is able to measure particle charge above 1,500 elementary charges of either polarity. Simulations show that for microparticles having a size and density close to that which is expected for Mars dust, the device is able to ideally measure the mass of particles ranging from 0.2–2.5 μm in diameter, providing broad coverage of particles too small to be observed by optical scattering and other techniques that have been previously used on Mars.

This thesis presents a theoretical and experimental investigation of the interaction of electronically excited Rydberg hydrogen atoms with metal surfaces and the associated charge-transfer process. As a Rydberg atom approaches a metal surface, the energies of the Rydberg states are perturbed by the surface potential generated by the image charges of the Rydberg electron and core. At small atom-surface separations, the Rydberg atom may be ionised by resonant charge transfer of the Rydberg electron to the continuum of delocalised unoccupied metal states, with which the Rydberg electron is degenerate in energy. Typically, this ‘surface ionisation’ can be measured by extracting the remaining positively charged ion-cores with externally applied electric fields. By applying various levels of theory, from classical to fully time-dependent quantum calculations, this thesis explores various experimentally relevant effects on the charge-transfer process, such as the magnitude and direction of the externally applied electric field, the atom collisional velocity, the presence of local surface stray fields and electronically structured surfaces. The theoretical results give insight into the previous experimental work carried out for the xenon atom and hydrogen molecule, and point out some of the fundamental differences from the hydrogen atom system. Experiments involving Rydberg hydrogen atoms incident on an atomically flat gold surface, a rough machined aluminium surface and a single crystal copper (100) surface are presented, providing for the first time the opportunity to make a quantitative comparison of theory and experiments. The ability to control the critical distance at which charge-transfer occurs is demonstrated by using Rydberg states of varying dimensions and collisional velocities. By changing the collisional angle of the incident Rydberg beam, the effect of Rydberg trajectory is also investigated. By manipulating the polarisation of the Rydberg electron with electric fields, genuine control over the orientation of the electron density distribution in the charge-transfer process is demonstrated. This property was predicted by the theory and should be unique to the hydrogen atom due to its intrinsic symmetry. By reversing the direction of the electric field with respect to the metal surface, electrons rather than positive ions are detected, with ionisation dynamics that appear to be very different, as predicted by quantum calculations. Experiments involving the single crystal Cu(100) surface also suggests possible resonance effects from image states embedded in the projected bandgap which are shown from quantum calculations to play an important role in the surface charge transfer of electronically structured metal substrates. The experimental technique developed in this work provides some exciting future applications to study quantum confinement effects with thin films, nanoparticles and other bandgap surfaces. The ability to control the Rydberg orbital size, electronic energy, collisional velocity and orientation in the charge-transfer process will provide novel ways of probing the surface’s electronic and physical structure, as well as being a valuable feature in offering new opportunities for controlling reactive processes at metallic surfaces.

Image charge detection is presented as a possible candidate to realise deterministic ion implantation. The deterministic placement of single impurities in solid substrates will enable a variety of novel applications, using their quantum mechanical properties for sensors or qubit registers. In this work, experimental techniques are used together with theoretical calculations to develop, characterise and optimise the detection of charged objects in a single pass through an image charge detector. In the main experimental part, ion bunches are employed as a model system for highly charged ions in proof-of-principle measurements with detector prototypes built in our labs. Image charge signals are characterised in the time and frequency domain. Using a statistical measurement and data analysis protocol, the noise and signal probability density functions are determined to calculate error and detection rates. It was found that even at an extremely low signal-to-noise ratio of 2, error rates can be suppressed effectively for high fidelity implantation. Aiming to improve the sensitivity, the maximum possible signal-to-noise ratio is calculated and discussed in dependence on the design parameters of an optimised image charge detector and the kinetic ion parameters. Lastly, a new ion implantation set-up combining focused ion beam technology with a source able to produce highly charged ions is introduced.

Le travail de cette thèse porte sur l’étude expérimentale de la diffusion d’atomes d’hydrogène sur des surfaces et sous incidence rasante. L’énergie des atomes et des ions varie de quelques centaines d’eV à quelques keV, tandis que les surfaces étudiées sont des isolants et des semi-métaux. En particulier on a étudié la formation de l’ion H- sur du graphite pyrolytique dit HOPG (highly oriented pyrolytic graphite) et sur une surface de LiF(001). Pour ce dernier système, nous avons étudié en détail la diffraction d’atomes H° et d’ions H+. Ces expériences ont été réalisées sur un montage expérimental utilisant un faisceau pulsé et permettant de détecter en coïncidence les particules diffusées et les électrons secondaires. L’ensemble permet de connaître la charge finale de la particule diffusée, sa perte d’énergie, son angle de diffusion, le tout en corrélation avec la statistique et l’énergie des électrons émis.Le résultat de ce travail a révélé que la diffraction persiste dans le régime inélastique. En effet, nous observons un motif de diffraction après la neutralisation de proton sur la surface de LiF(001). Un modèle est proposé pour expliquer ces résultats qui semblent en contradiction avec ceux publiés par le groupe de H. Winter sur la diffraction d’atomes d’hydrogène sur cette même surface. Concernant la formation d’ion négatif sur HOPG, nous avons mis en évidence un taux de H- (~10%) sur une surface propre. C’est le plus haut taux de H- jamais observé avec ce type d’expérience en incidence rasante. C’est encore plus élevé qu’avec des isolants ioniques, ces derniers donnant un taux déjà 10 fois plus grand que celui observé sur métaux propres. Ces résultats confirment l’efficacité du graphite à convertir des ions et des atomes en ions négatifs. En exploitant les données fournies par la technique des coïncidences, nous avons pu élucider le mécanisme à l’œuvre dans cette conversion. Du fait de la structure électronique particulière de HOPG, avec une bande interdite projetée dans la direction Gamma, seuls les électrons localisés sigma contribuent à la formation de l’ion négatif, donnant au HOPG un caractère isolant du point de vue de la capture électronique. Les électrons pi contribuant de manière efficace à la perte d’énergie par collisions binaires, donnant de ce point de vue au HOPG son caractère métallique. / In this thesis, we have investigated experimentally the scattering of hydrogen atoms and ions on solid surfaces at grazing incidence. The projectile energy ranges from several hundred eV to few keV. The formation of H- ions is studied on highly oriented pyrolytic graphite (HOPG) surface; and surface diffraction is carried out on LiF(001) surface with H° and H+ particle scattering. Both experiments were performed in the same experimental setup (see Figure 1.2 and 2.1)—with grazing scattering geometry and a PSD (position sensitive detector) located downstream to record scattered particles. For charge state analysis a set of electrostatic plates is inserted between sample and PSD. During the experiment, coincident measurement technique is used to identify the energy loss associated to 0, 1, 2…electrons emission. Clear evidence of diffraction with inelastic scattering by proton on LiF(001) has been obtained, which has not been observed before. Indeed, the group of H. Winter reported that no diffraction exists with inelastic scattering of H° on LiF(001). However, according to our result, a coherence scattering factor still exists even though the electron capture by the proton is an inelastic process. For negative ion formation on HOPG surface, we report here the highest fraction of H- (~10%) measured in grazing scattering experiments; it is larger than those obtained on ionic insulators, the latter being typically 10 times larger than those measured on clean metals. These results confirm the high yields of negative hydrogen ions from graphite reported in the literature. Electron emission and energy loss of scattered beam have also been deciphered via coincidence measurement. Due to the special structure of HOPG, two kinds of electron emissions (σ and π-band electron) and energy losses (cycles and metal-like energy loss) have been measured. Furthermore, the total electron emission on HOPG with insulator-like behavior and total energy loss with metal-like are the most representative property of HOPG which have been first presented in this thesis.

Im Folgenden werden Transferprozesse in Nanohybridsystemen theoretisch untersucht. Diese Hybridsysteme sind vielversprechende Kandidaten für neue optoelektronische Anwendungen und erfahren daher ein erhebliches Forschungsinteresse. Jedoch beschränken sich Arbeiten darüber hauptsächlich auf experimentelle Untersuchungen und kaum auf die dazugehörige theoretische Beschreibung. Bei den theoretischen Betrachtungen treten entscheidende Limitierungen auf. Es werden entweder Details auf der atomaren Ebene vernachlässigt oder Systemgrößen betrachtet, die wesentlich kleiner als im Experiment sind. Diese Thesis zeigt, wie die bestehenden Theorien verbessert werden können und erweitert die bisherigen Untersuchungen durch die Betrachtung von vier neuen hoch relevanten Nanohybridsystemen. Das erste System ist eine Nanostruktur, die aus einem Au-Kern und einer CdS-Schale besteht. Beim zweiten System wurde eine ZnO/Para-Sexiphenyl Nanogrenzfläche untersucht. Die zwei anderen Systeme beinhalten jeweils einen CdSe-Nanokristall, der entweder mit einem Pheophorbide-a-Molekül oder mit einem röhrenförmigen Farbstoffaggregat wechselwirkt. In allen Systemen ist der Anregungsenergie-Transfer ein entscheidender Transfermechanismus und steht im Fokus dieser Arbeit. Die betrachteten Hybridsysteme bestehen aus zehntausenden Atomen und machen daher eine individuelle Berechnung der einzelnen Subsysteme sowie deren gegenseitiger Wechselwirkung notwendig. Die Halbleiter-Nanostrukturen werden mit der Tight-Binding-Methode und der Methode der Konfigurationswechselwirkung beschrieben. Für das molekulare System wird die Dichtefunktionaltheorie verwendet. Die dazugehörigen Rechnungen wurden von T. Plehn ausgeführt. Das metallische Nanoteilchen wird durch quantisierte Plasmon-Moden beschrieben. Die verwendeten Theorien ermöglichen eine Berechnung von Anregungsenergietransfer in Nanohybridsystemen von bisher nicht gekannter Systemgröße und Detailgrad. / In the following, transfer phenomena in nanohybrid systems are investigated theoretically. Such hybrid systems are promising candidates for novel optoelectronic devices and have attracted considerable interest. Despite a vast amount of experimental studies, only a small number of theoretical investigations exist so far. Furthermore, most of the theoretical work shows substantial limitations by either neglecting the atomistic details of the structure or drastically reducing the system size far below the typical device extension. The present thesis shows how existing theories can be improved. This thesis also expands previous theoretical investigations by developing models for four new and highly relevant nanohybrid systems. The first system is a spherical nanostructure consisting of an Au core and a CdS shell. By contrast, the second system resembles a finite nanointerface built up by a ZnO nanocrystal and a para-sexiphenyl aggregate. For the last two systems, a CdSe nanocrystal couples either to a pheophorbide-a molecule or to a tubular dye aggregate. In all of these systems, excitation energy transfer is an essential transfer mechanism and is, therefore, in the focus of this work. The considered hybrid systems consist of tens of thousands of atoms and, consequently, require an individual modeling of the constituents and their mutual coupling. For each material class, suitable methods are applied. The modeling of semiconductor nanocrystals is done by the tight-binding method, combined with a configuration interaction scheme. For the simulation of the molecular systems, the density functional theory is applied. T. Plehn performed the corresponding calculations. For the metal nanoparticle, a model based on quantized plasmon modes is utilized. As a consequence of these theories, excitation energy transfer calculations in hybrid systems are possible with unprecedented system size and complexity.