Determining the electric quadrupole moments of gas molecules from measurements of birefringence induced in the gas by an applied electric field gradient is widely recognised as being the most direct experimental technique for this purpose. This thesis presents a new molecular theory of the experiment, and also describes the apparatus used in the measurement of the quadrupole moments of a number of gases and the revisions made to the manner in which the experiment was performed. A recent eigenvalue theory of light propagation in matter has been used to derive an expression relating the induced birefringence to the electric quadrupole moment of the molecule, whether this be dipolar or not. This expression is different from that which has previously been applied to dipolar molecules. It is shown that the new expression is independent of molecular origin only if it is cast in terms of the primitive quadrupole moment, as opposed to the traceless moment. Previous work using the same set of apparatus yielded results for carbon dioxide which were significantly lower than those reported by other workers. By using the Jones calculus to re-examine the cascade of optical components used in the experiment, it was found that the previous method of performing the experiment did not completely eliminate the effects of an imperfect retardance in the quarter-wave plate used, nor of strain-induced birefringence in the windows of the the cell containing the gas. These effects could cause results to be underestimated by as much as 8%. It is shown that a better method of performing the experiment is to amplify the optical signal by deliberately offsetting the analysing prism, rather than the quarter-wave plate as was previously done. The results of measurements made using this technique are reported for carbon dioxide, carbon monoxide, nitrogen, ethene, chlorine, and boron trifluoride. The measured quadrupole moment of carbon dioxide is in good agreement with the most recent values found by other workers using a similar experiment, and with the latest theoretical value of this quantity. / Thesis (PH.D.)-University of Natal, Pietermaritzburg, 1993.

No description available.

The three-dimensional quadrupole ion trap (QIT) is an extraordinary device. It functions both as an ion store in which gaseous ions can be confined for a period of time and as a mass spectrometer of considerable mass range and variable mass resolution. Over the past few decades, it has evolved into a powerful tool for both research and routine analysis. The basic objective of this thesis is the development of a three-dimensional quadrupole ion trap with cylindrical symmetry in laminar approximation. The laminar construction allows hyperbolic geometry to be well approximated with minimal construction effort and also provides more access into the trap through interlaminar spaces without disruption of the field. The performance of the trap is examined in the mass selective trapping mode and mass-selective instability mode. Fourier detection is also done. Resolution of our instrument is limited by the external hardware. There is not good enough data quality and so not a good enough spectrum to predict its resolution accurately. A few changes to the instrumentation of the trap will improve the resolution.

Estudamos a parte dipolo-quadrupolo da energia de interação entre dois sistemas neutros, para distâncias intermediárias e grandes em relação às dimensões lineares dos mesmos / We study the dipole-quadrupole parto f the interaction energy between two neutral systems for intermediary distances and large distances in relation to its linears dimensions

Thesis (Ph.D.)--Boston University. / Hartree-Fock self-consistent field calculations of the Roothaan (linear combination of atomic orbitals - molecular orbital) type have been carried out on an electronic computer for LiH and Li2 using an extended basis set of Slater type atomic orbitals. Configuration interaction calculations result in a total molecular energy of 99.34% of the experimental value, and a dissociation energy of 89.33% of the experimental value in LiH. Similar calculations in Li2 result in 99.40% and 89.9%, respectively, for these two numbers. The energy of atomic Li, which enters the dissociation energy calculation, is calculated to comparable accuracy (99.42%). [TRUNCATED]

Estudamos a parte dipolo-quadrupolo da energia de interação entre dois sistemas neutros, para distâncias intermediárias e grandes em relação às dimensões lineares dos mesmos / We study the dipole-quadrupole parto f the interaction energy between two neutral systems for intermediary distances and large distances in relation to its linears dimensions

Cette thèse présente la production d'un gaz dégénéré de rubidium 87 dans le régime quasibidimensionnel (2D) et l'étude des modes collectifs de ce gaz. Nous montrons que le gaz quasi-2D peut être amené en dessous du seuil de la transition Berezinskii-Kosterlitz-Thouless. Nous montrons le caractère superfluide du gaz dégénéré par la présence des modes quadrupolaire et ciseaux, dont nous mesurons les fréquences d'oscillation. Son caractère bidimensionnel est vérifié par la mesure de la fréquence du mode monopolaire. Nous mettons en évidence l'influence du confinement transverse et de la troisième dimension sur la fréquence de ce mode. Pour produire le superfluide, un condensat de Bose-Einstein est d'abord produit dans un piège quadrupolaire bouché par un faisceau laser très désaccordé et soigneusement optimisé pour réduire les pertes Majorana par renversement de spin. Le condensat est ensuite transféré vers un « piège habillé », c'est-à-dire un potentiel adiabatique dans lequel les atomes sont habillés par un champ radiofréquence. Pour rendre le piège plus anisotrope, le gradient magnétique est augmenté au maximum, ce qui nous permet d'explorer le régime quasi-2D pour le gaz de Bose. Les deux types de piège utilisés sont caractérisés en détail. Nous tirons parti de la souplesse du potentiel adiabatique pour exciter et étudier les modes collectifs. / This thesis presents the production of a degenerate rubidium 87 gas in the quasi two-dimensional (2D) regime and the study of collective modes of this gas. We show that the gas can be prepared below the Berezinskii-Kosterlitz-Thouless transition threshold. The superfluid nature of the gas is demonstrated through the observation of the quadrupole and scissors modes. We measure their oscillation frequencies. The bidimensional character of the gas is evidenced through the measurement of the monopole mode frequency. We show the influence of the third, hidden, dimension on this oscillation frequency. In order to produce the superfluid, a Bose-Einstein condensate is first produced in a magnetic quadrupole trap plugged by a far off-resonance laser beam, carefully optimized to overcome Majorana spin ip losses. The condensate is then transferred to the “ dressed trap “, i.e. the adiabatic potential seen by the radiofrequency dressed atoms. We ramp up the magnetic gradient to its maximum value in order to increase the trap anisotropy, and eventually reach the quasi-2D regime for the Bose gas. The two kinds of trap used are characterized in detail. We take advantage of the adiabatic potential smoothness in order to excite and study the collective modes.

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Relative Orientation of EFG Tensors of Half-integer Quadupolar Nuclei Studied by 3D MQMAS Spin Diffusion Spectroscopy

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.