Heat transport by phonons and magnons in crystals due to a local perturbation in temperature is described by the Boltzmann transport equation. In this project a one phonon one magnon system was studied in a one dimensional rod with reflective boundaries. Using the splitting algorithm the problem was reduced to a transport and collision term. The resulting stabilization time for a initial phonon and magnon distribution and the respective temperatures at equilibrium was calculated. This study shows how energy propagates in crysials and gives further understanding of how the coupling of phonons and magnons affect heat transport.

Atom-surface interactions are becoming an integral part of the field of atom optics. Here the role of van der Waals atom-surface interactions in atom wave diffraction and interferometry are investigated. In particular, it is shown that van der Waals interactions influence the intensity and phase of atomic diffraction patterns obtained from material gratings. As a result the atomic diffraction patterns are utilized to make an accurate determination of the interaction strength and verify the spatial variation of the atom-surface potential. A theory for describing the modified atom wave diffraction patterns is developed through an analogy with optical waves. An atom interferometer is used to directly measure the de Broglie wave phase shift induced by atom-surface interactions. More specifically, the phases of the zeroth, first, and second diffraction orders are measured. A proposal for using electromagnetic fields to modify the van der Waals interaction is put forth. Several of the important experimental components for observing such an effect are also demonstrated.

Stuttgart, Univ., Diss., 2003.

Call number: LD2668 .T4 1978 R52 / Master of Science

No description available.

No description available.

The synthesis, characterization and coordination chemistry of novel zwitterionic late transition metal complexes has been carried out, and an investigation of their ability to act as olefin polymerisation catalysts has been conducted. These systems are based on 6- aminofulvene-2-aldiminate ligands (R2AFA¯) which are capable of binding metal centres via two nitrogen donors, delocalising the negative charge into their cyclopentadienyl moiety, thus resulting in the formation of neutral zwitterionic complexes. Preparation and characterisation of mono- and di-substituted complexes such as Ph2AFACuPPh3, (Ph2AFA)2Zn, (Ph2AFA)2Co, (Ph2AFA)2Ni and (Ph2AFA)2Pd have revealed that this type of ligand has enough flexibility to distort upon coordination to the metal depending on geometrical or steric restrictions. As a result, when the ligand coordination involves narrow binding angle of the metal chelate, as it happens in the square-planar species, a severe loss of planarity of the ligand framework is observed, in contrast with the tetrahedral structures where such binding angles are wider. Although the coordination of the ligand primarily occurs through the nitrogen donors, once they have been occupied by the metal centre, it is possible to exploit the aromatic Cp ring for coordination to a Cp*Ru+ unit. In this way, the synthesis and characterisation of two- and tri-metallic complexes [(Cp*Ru)(Ph’2AFA)Pd(η3-C3H5)][BF4] (where Ph’= 2,4,6-trimethylphenyl) and [(Cp*Ru)2(Ph2AFA)2Pd][BF4]2 has been achieved, featuring the R2AFA¯ molecule acting as an ambidentate ligand, binding the palladium atom in a diimine fashion and the ruthenium centres by means of the C5 ring. The synthesis of the complex Cp*RuPh2AFA where the two N atoms are vacant was also achieved and it was found that this compound acts as a proton sponge in the presence of protic solvents. In an effort to prepare AFA-metal complexes which could be of potential use in olefin polymerisation catalysis, two novel species, [(Ph2AFA)Pd(Me)PPh3] and [(Ph’2AFA)Pd(C3H5)] (where Ph’= 2,4,6-trimethylphenyl) have been synthesised and characterised, and polymerisation tests with ethylene have been carried out. Some preliminary screening of other molecules as monomers for polymerisation catalysis has also been conducted.

Decoherence due to photon scattering in an atom interferometer was studied as a function of laser frequency near an atomic resonance. The resulting decoherence (contrast-loss) spectra will be used to calibrate measurements of tune-out wavelengths that are made with the same apparatus. To support this goal, a theoretical model of decoherence spectroscopy is presented here along with experimental tests of this model.

I used a Mach-Zehnder atom interferometer to measure the static electric-dipole polarizabilities of K, Rb, and Cs atoms with 0.11\% uncertainty. Static polarizability measurements serve as benchmark tests for 𝑎𝑏 𝑖𝑛𝑖𝑡𝑖𝑜 atomic structure calculations. Calculating atomic properties such as polarizabilities, van der Waals coefficients, state lifetimes, or oscillator strengths involves accurately calculating the valence electrons' electric-dipole transition matrix elements. Additionally, testing Cs atomic structure calculations helps interpret the results of parity non-conservation experiments, which in turn places constraints on beyond-the-standard-model physics. I discuss improvements to our experiment that allowed us to measure static polarizabilities with 0.11% uncertainty, and we present our results in the context of recent 𝑎𝑏 𝑖𝑛𝑖𝑡𝑖𝑜 and semi-empirical static polarizabilities and recent, high-precision measurements of excited state lifetimes and van der Waals C₆ coefficients. I also used our interferometer to develop a new technique for inertial sensing. High precision, portable, atom-interferometer gyroscopes and accelerometers are desirable for self-contained inertial navigation and in the future may be used for tests of General Relativity and searches for gravitational waves using satellite-mounted inertial sensors. Satellite-mounted atom interferometers are challenging to build because of size, weight, power, and reliability constraints. Atom interferometers that use nanogratings to diffract atoms are attractive for satellite-mounted inertial sensing applications because nanogratings weigh approximately nothing and require no power. We developed a new 𝑖𝑛 𝑠𝑖𝑡𝑢 measurement technique using our nanograting atom interferometer, and we used it to measure inertial forces for the benefit of our static polarizability measurements. I also review how to calculate the sensitivity of a nanograting atom interferometer, and I employed these calculations in order to design a portable, nanograting atom interferometer inertial sensor.

Neste trabalho, descrevemos os conceitos de alinhamento e orientação baseados no formalismo de Fano e Macek e estudamos a fotoionização do estado fundamental do átomo de Hélio. Para isso usou-se uma função de onda aproximada obtida a partir da diagonalização do operador de Gailitis- Damburg. A anisotropia do sistema formado após a colisão foi caracterizada através do cálculo da densidade eletrônica do íon e através do tensor de alinhamento e do vetor de orientação. O comportamento destes parâmetros para as transições n? -> 1s e n->n-1 em função de n (número quântico principal do íon) foi graficado para as duas simetrias relevantes, 1P° e 3P°. Observamos que o alinhamento máximo do sistema, em relação ao eixo de maior simetria definido como sendo o eixo z ocorre no limite de Wannier (n-> ?). Nesta situação o elétron iônico se encontra ao longo do eixo z para a simetria 3 P° e perpendicular ao eixo z para a simetria 1 P°. Esse fenômeno é causado pela interação elétron-elétron / In this work we describe the concepts of aligrnment and orientation based on the formalism of Fano and Macek formalism and we study the photoionization of the Helium atom ground state. We have used an approximate wave function obtained from the diagonalization of the Gailitis- Damburg operator. The anisotropy of the system formed after the colision was measured through the calculation of the ion electronic density and also by the use of the alignment tensor and orientation vector. The behaviour of these parameters for the transitions np ->1s and n ->n-1 as a function of n (the principal quantum number of the ion) was plotted for both the relevant symmetries, 1 P° and 3 P°. We have observed that the maximum alignment of the system, with respect to the dominant symmetry axis defined as the z axis, occurs in the Wannier threshold (n->?). This leads to the alignment of the ionic electron along the z axis for the 3 P°symmetry, and orthogonal to the z axis for the 1P° symmetry. This phenomenom is caused by the electron-electron Ínteraction.