When a particle is illuminated by a beam of light it will scatter and redistribute the light in all directions. How it scatters depends on the size, shape and refractive index of the particle. Additionally, it depends on the wavelength and polarization of the illuminating beam. The direction and distance to the observer relative the particle also needs to be considered.  A digital holographic imaging system is used to collect parts of the scattered light from micrometer-sized particles. By utilizing digital holography a three-dimensional reconstruction of the imaged scene is possible. Traditionally, particles are localized based on the intensity in the holographic reconstructions. In this licentiate thesis, the phase response of the scattered light is investigated and utilized. An alternative method for locating spherical particles is presented. The method locate particles based on a simple feature of a propagating wave, namely the fact that the wavefront curvature changes from converging to diverging at the axial location of the particle. The wavefront curvature is estimated using two different methods. The first method estimates the lateral phase-gradients using a finite-difference method. The second method uses a three-dimensional parametric model based on a Chebyshev polynomial expansion. The methods are demonstrated using both simulations and experimental measurements. The simulations are based on the Lorenz-Mie scattering theory for spherical particles and are combined with an imaging system model. Experiments are performed using an off-axis polarization sensitive digital holographic system with a coherent Nd:YAG laser. Measurements of stationary particles are made to validate and evaluate the proposed method. It is found that these methods estimate the true axial position and does not have the offset that is associated with intensity-based methods. Additionally, it is possible to exclude noise that shows up as false particles since noise does not have the same phase response as a real particle. The second method, that uses a parametric model, also improves the standard deviation in the positioning.

Bose-Einstein condensates of dilute gases provide a rich and versatile platform to study both single-particle and many-body quantum phenomena. This thesis describes several experiments using a Bose-Einstein condensate of Rb-87 as a model system to study novel matter-wave effects that traditionally arise in vastly different systems, yet are difficult to access. We study the scattering of a particle from a repulsive potential barrier in the non-asymptotic regime, for which the collision dynamics are on-going. Using a Bose-Einstein condensate interacting with a sharp repulsive potential, two distinct transient scattering effects are observed: one due to the momentary deceleration of particles atop the barrier, and one due to the abrupt discontinuity in phase written on the wavepacket in position-space, akin to quantum reflection. Both effects lead to a redistribution of momenta, resulting in a rich interference pattern that may be used to reconstruct the single-particle wavefunction. In a second experiment, we study the response of a particle in a periodic potential to an applied force. By abruptly applying an external force to a Bose-Einstein condensate in a one-dimensional optical lattice, we show that the initial response of a particle in a periodic potential is in fact characterized by the bare mass, and only over timescales long compared to that of interband dynamics is the usual effective mass an appropriate description. This breakdown of the effective mass description on fast timescales is difficult to observe in traditional solid state systems due to their large bandgaps and fast timescale of interband dynamics. Both these experiments make use of the condensate's long coherence length, and the ability to shape and modulate the external potential on timescales fast compared to the particle dynamics, allowing for observation of novel matter-wave effects.

Bose-Einstein condensates of dilute gases provide a rich and versatile platform to study both single-particle and many-body quantum phenomena. This thesis describes several experiments using a Bose-Einstein condensate of Rb-87 as a model system to study novel matter-wave effects that traditionally arise in vastly different systems, yet are difficult to access. We study the scattering of a particle from a repulsive potential barrier in the non-asymptotic regime, for which the collision dynamics are on-going. Using a Bose-Einstein condensate interacting with a sharp repulsive potential, two distinct transient scattering effects are observed: one due to the momentary deceleration of particles atop the barrier, and one due to the abrupt discontinuity in phase written on the wavepacket in position-space, akin to quantum reflection. Both effects lead to a redistribution of momenta, resulting in a rich interference pattern that may be used to reconstruct the single-particle wavefunction. In a second experiment, we study the response of a particle in a periodic potential to an applied force. By abruptly applying an external force to a Bose-Einstein condensate in a one-dimensional optical lattice, we show that the initial response of a particle in a periodic potential is in fact characterized by the bare mass, and only over timescales long compared to that of interband dynamics is the usual effective mass an appropriate description. This breakdown of the effective mass description on fast timescales is difficult to observe in traditional solid state systems due to their large bandgaps and fast timescale of interband dynamics. Both these experiments make use of the condensate's long coherence length, and the ability to shape and modulate the external potential on timescales fast compared to the particle dynamics, allowing for observation of novel matter-wave effects.

The Alpha Particle X-ray Spectrometer (APXS) on the Mars Exploration Rovers possesses the ability to detect carbon and oxygen within martian samples via Rutherford backscattering principles. Several consecutive measurements of the martian atmosphere by Spirit, paralleled by Monte Carlo simulations, provided an energy calibration to mitigate the absence of an alpha-mode calibration pre-flight. Data from a pre-flight thermal acceptance test agreed with this energy calibration, confirming the presence of an unexpected offset. Correcting a bug in the APXS firmware resulted in a temperature-independent energy scale. A model was developed and applied to all atmospheric data illustrating a dip in atmospheric peak areas, potentially arising from a week-long weather event on Mars. An early expansion of this model to solid samples has not yet been able to detect any hydrated minerals or carbonates. Preliminary investigations into determining martian atmospheric pressure and potential elemental layering within samples shows promise.

The thesis deals with quantum reaction dynamics of three-particle systems. The thesis summarizes main theoretical results about three-body problem in quantum mechanics. A simple two dimensional model of three-particle system corresponding to atom-diatom collision was studied as a part of this thesis. The model allows for vibrational excitation and reaction processes. Solution based on distorted-wave method and Schwinger variational principle is proposed to solve the model. Proposed method of solution is then applied to a system of three coupled Morse potential energy surfaces. Probabilities of possible proces- ses depending on energy of incoming particle were calculated using the proposed method of solution for two variants of coupled Morse PESs. 1

The utilization of thermal fluctuations or Johnson/Nyquist noise as a spectroscopic method to determine transport properties in conductors or semiconductors is developed in this paper. The autocorrelation function is obtained from power spectral density measurements thus enabling electronic transport property calculation through the Green-Kubo formalism. This experimental approach is distinct from traditional numerical methods such as molecular dynamics simulations, which have been used to extract the autocorrelation function and directly related physics only. This work reports multi-transport property measurements consisting of the electronic relaxation time, resistivity, mobility, diffusion coefficient, electronic contribution to thermal conductivity and Lorenz number from experimental data. Double validation of the experiment was accomplished through the use of a standard reference material and a standard measurement method, i.e. four-probe collinear resistivity technique. The advantages to this new experimental technique include the elimination of any required thermal or potential gradients, multi-transport property measurements within one experiment, very low error and the ability to apply controlled boundary conditions while gathering data. This research has experimentally assessed the gas pressure and flow effects of helium and argon on 30 nm Au and Cu thin films. The results show a reduction in Au and Cu electronic thermal conductivity and electrical resistivity when subjected to helium and argon pressure and flow. The perturbed electronic transport coefficients, attributed to increased electron scattering at the surface, were so dominant that further data was collected through straight-forward resistance measurements. The resistance data confirmed the thermal noise measurements thus lending considerable evidence to the presence of thin film surface scattering due to elastic and inelastic gas particle scattering effects with the electron ensemble.

We calculate tree-level scattering amplitudes in φ^3 theory and Yang-Mills theory by means of the perturbiner expansion. This involves solving the Euler-Lagrange equations of motion perturbatively via a multi-particle ansatz, and using Berends-Giele recursion relations to extract the solution from simple on-shell data. The results are Berends-Giele currents which are then used to calculate the scattering amplitudes. The theoretical calculations are implemented into a Mathematica script which effectively handles recursive calculations and allows us to calculate amplitudes for an arbitrary number of particles.

Doctor of Philosophy / Department of Physics / Uwe Thumm / The time-dependent Schrödinger equation is integrated on a numerical lattice for up to three-dimensional problems. The wave packet propagation technique has been applied to ion – atom collisions in a strong laser field, the vibrational nuclear motion in small homonuclear diatomic molecular ions, and for the scattering of an ion in front of a metallic surface. For laser-assisted proton – hydrogen collisions it is shown, that strong circularly polarized radiation significantly alters the capture and ionization probabilities and results in a dichroism with respect to the helicity. In a pump – control – probe scheme, “stroboscopic” exposure of a nuclear wave packet of the deuterium molecular ion by a single or a series of short and intense laser control pulses may be used to produce an almost stationary distribution of a single vibrational level, where the nodal structure can be tested using the Coulomb explosion imaging technique. Using a pump – probe setup with variable probe delays it is proposed to use Fourier analysis of the time dependence of the Coulomb explosion kinetic energy release spectrum to reveal insight into the initial vibrational state distribution for small diatomic molecules. A last application demonstrates, that resonant charge transfer for scattering of a negative hydrogen anion on a metal surface depends crucially on the position of surface and image states relative to the conduction and valence band, thereby implying different reaction mechanisms for different surface cuts of a metal.

Two rich and vibrant fields of investigation - graphene and plasmonics - strongly overlap in this work, giving rise to a novel hybrid photodetection device. The intrinsic photoresponse of graphene is significantly enhanced by placing the gold nanorods exhibiting unique anisotropic localized surface plasmon resonances on the graphene surface. The reported enhanced photoresponse of graphene is caused by the redistribution of localized surface plasmons in the nanoparticles into graphene. The exact underlying energy redistribution mechanism is thoroughly studied by a single particle scattering spectroscopy monitoring the particle plasmon linewidth as a function of the number of underlaying graphene layers. The obtained extraordinary plasmon broadening for nanoparticles placed on graphene suggests the contribution of a novel energy redistribution channel attributed to the injection of hot electrons from gold nanorods into graphene.

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