Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Douglas J. Doren, Dept. of Chemistry and Biochemistry. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Includes bibliographical references (p. 197-212).

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Vita. Includes bibliographical references (leaves 116-130). Also available in electronic version.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 183-190).

Thesis (Ph. D.)--University of Oregon, 1999. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 95-97). Also available for download via the World Wide Web; free to University of Oregon users. Address:http://wwwlib.umi.com/cr/uoregon/fullcit?p9957570.

Made available in DSpace on 2016-05-17T16:50:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-28. Added 1 bitstream(s) on 2016-05-17T16:54:29Z : No. of bitstreams: 1 000855783.pdf: 748037 bytes, checksum: 8eabecae788e64f7c338bab8817fe30f (MD5) / Nesta dissertação apresentaremos uma revisão sobre as definições de tempos de tunelamento no contexto da Mecânica Quântica não-relativíıstica mais discutidas na literatura; proporemos uma generalização relativística para uma delas e compararemos nossos resultados com aqueles já conhecidos / In this dissertation we show a review about the most discussed definitions of quantum tunelling times in the context of Nonrelativistic Quantum Mechanics, we propose a relativistic generalization for one of them and compare our results with those well-known ones

abstract: The study of high energy particle irradiation effect on Josephson junction tri-layers is relevant to applications in space and radioactive environments. It also allows us to investigate the influence of defects and interfacial intermixing on the junction electrical characteristics. In this work, we studied the influence of 2MeV Helium ion irradiation with doses up to 5.2×1016 ions/cm2 on the tunneling behavior of Nb/Al/AlOx/Nb Josephson junctions. Structural and analytical TEM characterization, combined with SRIM modeling, indicates that over 4nm of intermixing occurred at the interfaces. EDX analysis after irradiation, suggests that the Al and O compositions from the barrier are collectively distributed together over a few nanometers. Surprisingly, the IV characteristics were largely unchanged. The normal resistance, Rn, increased slightly (<20%) after the initial dose of 3.5×1015 ions/cm2 and remained constant after that. This suggests that tunnel barrier electrical properties were not affected much, despite the significant changes in the chemical distribution of the barrier's Al and O shown in SRIM modeling and TEM pictures. The onset of quasi-particle current, sum of energy gaps (2&#916;), dropped systematically from 2.8meV to 2.6meV with increasing dosage. Similarly, the temperature onset of the Josephson current dropped from 9.2K to 9.0K. This suggests that the order parameter at the barrier interface has decreased as a result of a reduced mean free path in the Al proximity layer and a reduction in the transition temperature of the Nb electrode near the barrier. The dependence of Josephson current on the magnetic field and temperature does not change significantly with irradiation, suggesting that intermixing into the Nb electrode is significantly less than the penetration depth. / Dissertation/Thesis / M.S. Materials Science and Engineering 2012

Made available in DSpace on 2016-01-13T13:27:49Z (GMT). No. of bitstreams: 0 Previous issue date: 1992. Added 1 bitstream(s) on 2016-01-13T13:33:19Z : No. of bitstreams: 1 000524313.pdf: 4320286 bytes, checksum: 6ae85652f959edf2525a5a065a614b00 (MD5) / Discutimos nesta tese o efeito túnel através de uma barreira de potencial em várias dimensões e aplicamos a três problemas diferentes. Primeiramente estudamos o problema de tunelamento através de barreiras em duas dimensões usando métodos quânticos. Consideramos a colisão de dois isótopos de Ni à energias em torno da altura da barreira na região de 100 MeV. Encontramos os coeficientes de reflexão e transmissão fazendo um cálculo de canais acoplados. Nos cálculos numéricos consideramos até cinco canais abertos e encontramos que se o número de canais é aumentado, os resultados variam apenas ligeiramente. Propomos neste trabalho um tipo de acoplamento entre os graus de liberdade diferente daqueles existentes na literatura e estudamos o efeito deste acoplamento na região da barreira. Calculamos também a secção de choque de fusão e comparamos os nossos resultados com os experimentais e com outros encontrados na literatura. 0 segundo problema considerado é a emissão espontânea de núcleos mais pesados que a particula alfa. Discutimos a emissão de 'INTPOT. 14 C' do 'INTPOT. 223 Ra' que foi recentemente observada e calculamos os fatores de pré-formação. Estudamos a razão dos fatores de pré-formação para a emissão do 'INTPOT. 14 C' relativa à emissão da particula alfa do 'INTPOT. 223 Ra'. Consideramos uma barreira de potencial realistica, comparamos nossos resultados para os fatores de penetrabilidade e os fatores de pré-formação com outros encontrados recentemente na literatura. À seguir fazemos um estudo do tamanho do raio nuclear na teoria de decaimento exóticos, considerando as várias reações onde decaimentos de núcleos mais pesados que a particula alfa já foram observados. Finalmente, consideramos a formação de aglomerados alfa em núcleos. Usando um modelo de cluster simples, estudamos algumas propriedades nucleares do 'INTPOT. 44 Ti', como por exemplo, as funções... / The quantum tunneling through a potential barrier in several dimensions is discussed and three diferent problems are studied. Firstly the tunneling problem through two dimensional barrieers is studied using quantum mechanical methods. We consider the collision of two Ni isotopos at energies near the top of the barrier of 100 Mev. The reflection and transmission coefficients are found through a coupled channel calculation. We have considered up to five open channels in the numerical calculations and have found that if the number of channels is increased further the results change only slightly. A different kind of coupling between the degrees of freedom from those found in the literature is proposed and the effect of this coupling in the barrier region is studied. The sub-barrier fusion reaction cross section is also calculated and our results are compared with the data and other results found in the literature. The second problem is the spontaneous emission of nuclei havier than the alpha particle. The emission of 'INTPOT. 14 C' from 'INTPOT. 223 Ra' recently observed is discussed and the penetrability factors are calculated. The ratio of the preformation factor for the'INTPOT. 14 C' emission relative to the emission of the alpha particles by the 'INTPOT. 223 Ra' is studied. Considering a realistic potential barrier we compare our results for penetrability factors and preformation factors with other recently found in the literature. Then, the size of the nuclear radius in the exotic decay theory is studied, considering several reactions where decays of nuclei heavier than the alpha particle have been observed. Finally the alpha clustering in nuclei is considered. Using a simple cluster model some nuclear properties of the 'INTPOT. 43 Ti' are studied, as wave functions, energy levei schemes and decay widths. Two different kinds of semiclassical approximations are considered to study the wave functions and the quantum...

Orientador: Bruto Max Pimentel Escobar / Coorientador: José Tadeu Teles Lunardi / Banca: Diogenes Galetti / Banca: Antônio Marcos Batista / Resumo: Nesta dissertação apresentaremos uma revisão sobre as definições de tempos de tunelamento no contexto da Mecânica Quântica não-relativíıstica mais discutidas na literatura; proporemos uma generalização relativística para uma delas e compararemos nossos resultados com aqueles já conhecidos / Abstract: In this dissertation we show a review about the most discussed definitions of quantum tunelling times in the context of Nonrelativistic Quantum Mechanics, we propose a relativistic generalization for one of them and compare our results with those well-known ones / Mestre

Orientador: Valdir Casaca Aguilera-Navarro / Resumo: Discutimos nesta tese o efeito túnel através de uma barreira de potencial em várias dimensões e aplicamos a três problemas diferentes. Primeiramente estudamos o problema de tunelamento através de barreiras em duas dimensões usando métodos quânticos. Consideramos a colisão de dois isótopos de Ni à energias em torno da altura da barreira na região de 100 MeV. Encontramos os coeficientes de reflexão e transmissão fazendo um cálculo de canais acoplados. Nos cálculos numéricos consideramos até cinco canais abertos e encontramos que se o número de canais é aumentado, os resultados variam apenas ligeiramente. Propomos neste trabalho um tipo de acoplamento entre os graus de liberdade diferente daqueles existentes na literatura e estudamos o efeito deste acoplamento na região da barreira. Calculamos também a secção de choque de fusão e comparamos os nossos resultados com os experimentais e com outros encontrados na literatura. 0 segundo problema considerado é a emissão espontânea de núcleos mais pesados que a particula alfa. Discutimos a emissão de 'INTPOT. 14 C' do 'INTPOT. 223 Ra' que foi recentemente observada e calculamos os fatores de pré-formação. Estudamos a razão dos fatores de pré-formação para a emissão do 'INTPOT. 14 C' relativa à emissão da particula alfa do 'INTPOT. 223 Ra'. Consideramos uma barreira de potencial realistica, comparamos nossos resultados para os fatores de penetrabilidade e os fatores de pré-formação com outros encontrados recentemente na literatura. À seguir fazemos um estudo do tamanho do raio nuclear na teoria de decaimento exóticos, considerando as várias reações onde decaimentos de núcleos mais pesados que a particula alfa já foram observados. Finalmente, consideramos a formação de aglomerados alfa em núcleos. Usando um modelo de "cluster" simples, estudamos algumas propriedades nucleares do 'INTPOT. 44 Ti', como por exemplo, as funções... / Abstract: The quantum tunneling through a potential barrier in several dimensions is discussed and three diferent problems are studied. Firstly the tunneling problem through two dimensional barrieers is studied using quantum mechanical methods. We consider the collision of two Ni isotopos at energies near the top of the barrier of 100 Mev. The reflection and transmission coefficients are found through a coupled channel calculation. We have considered up to five open channels in the numerical calculations and have found that if the number of channels is increased further the results change only slightly. A different kind of coupling between the degrees of freedom from those found in the literature is proposed and the effect of this coupling in the barrier region is studied. The sub-barrier fusion reaction cross section is also calculated and our results are compared with the data and other results found in the literature. The second problem is the spontaneous emission of nuclei havier than the alpha particle. The emission of 'INTPOT. 14 C' from 'INTPOT. 223 Ra' recently observed is discussed and the penetrability factors are calculated. The ratio of the preformation factor for the'INTPOT. 14 C' emission relative to the emission of the alpha particles by the 'INTPOT. 223 Ra' is studied. Considering a realistic potential barrier we compare our results for penetrability factors and preformation factors with other recently found in the literature. Then, the size of the nuclear radius in the exotic decay theory is studied, considering several reactions where decays of nuclei heavier than the alpha particle have been observed. Finally the alpha clustering in nuclei is considered. Using a simple cluster model some nuclear properties of the 'INTPOT. 43 Ti' are studied, as wave functions, energy levei schemes and decay widths. Two different kinds of semiclassical approximations are considered to study the wave functions and the quantum... / Doutor