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Multinuclear (tin-119, carbon-13, deuterium) NMR spin-lattice relaxation studies on organo-tin compoundsFrangou, Andrew January 1979 (has links)
The carbon-13, tin-119 and deuterium MR spectra of a number of organo tin compounds have been detected by direct observation. The compounds fall into two main classes consisting of organo tin hydrides and organo tin chlorides. Tin-119 spin-lattice relaxation data for and nBu.Sn were measured, the first three over a temperature range. Measurements of tin-119 values were carried out with proton decoupling using, the inversion-recovery technique. NOE factors were measured by comparing spectra resulting from continuous and gated proton decoupling. For the n-alkyl tin compounds the T1 and HOE data indicated contributions to the total rate arising from the dipole-dipole interactions of tin-119 with remote protons. The competing mechanism was spin-rotation. T1 values were typically less than 5 seconds. Measurements of tin-119 T1 values in the hydrides were complicated by the magnitude of ( >1500 Hz) and only for nBuuSnH and Ph SnH have T and HOE factors n been determined. Carbon-13 T measurements have been made for factors have been determined for the last four molecules. Segmental motion was apparent in the n-alkyl chains. For rotation of the phenyl groups about the tin-carbon bond was indicated and the ratio of D /D has been determined.2The spin-lattice relaxation time of over a range of temperature was measured and the quadrupole coupling ponstant of deuterium in the bond was estimated as 88 +/- 10 kHz. The variation of the tin-119 chemical shift of with temperature and concentration has been investigated and the data can be adequately explained in terms of monomer-dimer equilibrium. Equilibrium constants and the enthalpy for the dissociation of the dimer have been evaluated. The tin-119 T1 and NOE data for this molecule at 1.4 and 2.3 T indicated a significant contribution to the relaxation from a field dependent mechanism.
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Position-sensitive germanium detectors for gamma-ray tracking, imaging and polarimetryKhaplanov, Anton January 2010 (has links)
Modern germanium detectors are often manufactured with two-dimensionally segmented electrical contacts. Signals induced in each segment are read out simultaneously when a photon is detected. Detailed pulse shape analysis (PSA) of these signals allows to resolve positions of individual γ-ray interactions with a precision of at least a few mm. The track of a photon can then be reconstructed using γ-ray tracking. Using these techniques, highly efficient large-volume germanium detectors can replace detector systems where previously highly granulated detector arrays were required, and/or large fractions of photons had to be rejected. The ability to reconstruct the direction of an incoming photon and its scattering path makes it possible to use segmented detectors for γ-ray imaging and polarimetry. Doppler correction of photon energies in experiments where γ rays are emitted from fast ion beams can be greatly improved due to improved determination of the emission angle with respect to the beam. Furthermore, arrays of many detectors can be built without the need for conventional anticoincidence detectors for escape suppression. Instead, photons escaping a detector crystal can be tracked through neighbouring ones. In this work position reconstruction accuracy was evaluated for segmented detectors in a number of geometries in realistic applications. Particular emphasis has been put on the reconstruction of data sets containing events of arbitrary complexity in terms of the number of hit segments and interactions per segment. The imaging and polarization sensitivities of a single planar germanium pixel detector have been evaluated experimentally. In these measurements, photons absorbed in two, often adjacent, segments were reconstructed. Simulated interactions of γ-rays with the detectors of the proposed DESPEC germanium array were analysed yielding the position resolution obtainable in realistic experimental situations, as well as its dependence on photon energy, event complexity, noise and other sources of error. / <p>QC 20170222</p>
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The Photoproduction of Strangeness in ΓP → ΛK+Π+Π− with CLAS at Jefferson LabUnknown Date (has links)
The available information about strange excited mesons is limited and most of the observed states have been reported but not
confirmed. While the low mass region (1.0 - 1.5 GeV) has been extensively studied in the past and states such as the K1(1270), K1(1400),
and K*(1410) have been confirmed by a handful of experiments, little is known about the spin-parity structure of resonances in the higher
K+ π+ π- mass region (1.5-2.0 GeV). Past experiments have used hadron beams to gain access to the K+ π+ π- system, and have provided
extensive information about strange states that made mapping their spectrum possible. Except for the K*(892), none of the excited strange
states has been photoproduced before. We perform a partial wave analysis on a photoproduced K+ π+ π- system produced off a Λ baryon using
the CLAS detector at Jefferson Lab. Using a photon beam incident of a liquid hydrogen target, we are able to reconstruct 16K events of the
γ p -> Λ K+ π+ π- topology. Results from initial data selection confirmed the dominance of two decay modes for a K+ π+ π- resonance:
the K*(892)π+ and the ρ(770)K+. A PWA was carried out in the helicity formalism using the reflectivity basis in the isobar model to
parametrize the decay amplitudes of the resonances. Resonating structures are found in the 1+S wave primarily coupling to K*(892)π+ with a
mass of 1.35 GeV/c2 and to ρ(770)K with a lower mass structure around 1.33 GeV/c2 and a higher mass resonance around 1.73 GeV/c2. The 1-P
also exhibited a significant resonating behavior with a mass of 1.43 GeV/c2 coupling primarily to the K*(892)π+ decay mode. Also observed,
an enhancement around 1.49 GeV/c2 in the 2+D wave strongly coupling to K*2 (1430)π+, and an enhancement in the 2-S wave around 1.76 GeV/c2
coupling primarily to K*2 (1430)π+. / A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for
the degree of Doctor of Philosophy. / Spring Semester 2016. / April 11, 2016. / Data Analysis, Hadrons, KPiPi, Particle Physics, Photoproduction, PWA / Includes bibliographical references. / Paul Eugenio, Professor Directing Dissertation; James Justus, University Representative; Volker
Crede, Committee Member; Simon Capstick, Committee Member; Alexander Ostrovidov, Committee Member; Horst Wahl, Committee
Member.
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Relativistic Mean Field Models for Finite Nuclei and Neutron StarsUnknown Date (has links)
In this dissertation we have created theoretical models for finite nuclei, nuclear matter, and neutron stars within the framework of relativistic mean field (RMF) theory, and we have
used these models to investigate the elusive isovector sector and related physics, in particular, the neutron-skin thickness of heavy nuclei, the nuclear symmetry energy, and the
properties of neutron stars. To build RMF models that incorporate collective excitations in finite nuclei in addition to their ground-state properties, we have extended the
non-relativistic sum rule approach to the relativistic domain. This allows an efficient estimate of giant monopole energies. Moreover, we have combined an exact shell-model-like approach
with the mean-field calculation to describe pairing correlations in open-shell nuclei. All the ingredients were then put together to establish the calibration scheme. We have also extended
the transformation between model parameters and pseudo data of nuclear matter within the RMF context. Performing calibration in this pseudo data space can not only facilitate the searching
algorithm but also make the pseudo data genuine model predictions. This calibration scheme is also supplemented by a covariance analysis enabling us to extract the information content of a
model, including theoretical uncertainties and correlation coefficients. A series of RMF models subject to the same isoscalar constraints but one differing isovector assumption were then
created using this calibration scheme. By comparing their predictions of the nuclear matter equation of state to both experimental and theoretical constraints, we found that a small
neutron skin of about 0.16 fm in Pb208 is favored, indicating that the symmetry energy should be soft. To obtain stronger evidence, we proceeded to examine the evolution of the isotopic
chains in both oxygen and calcium. Again, it was found that the model with such small neutron skin and soft symmetry energy can best describe both isotopic chains, and the resultant values
of the neutron-skin thickness and the symmetry energy are consistent with most current constraints. Finally, we addressed the recent tension between dense matter theory and the observation
of neutron stars with rather small stellar radii. By employing Lindblom's algorithm, we were able to derive the underlying equation of state for assumed mass-radius relations having the
"common radius" feature followed by recent analyses. We found that, in order to support two-solar-mass neutron stars, the typical stellar radii must be greater than 10.7 km—barely
compatible with recent analyses—to prevent the underlying equation of state from violating causality. / A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2015. / October 30, 2015. / Includes bibliographical references. / Jorge Piekarewicz, Professor Directing Dissertation; David Kopriva, University Representative; Alexander Volya, Committee Member; Volker Crede,
Committee Member; Nicholas Bonesteel, Committee Member.
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Estudo do espalhamento elástico do ANTPOT.16O pelo ANTPOT.27 AL / Study of elastic scattering of \'ANTPOT.16O\' by \'ANTPOT.27 AL\'Crema, Edilson 09 August 1983 (has links)
Estudo do espalhamento elástico do ANTPOT.16O pelo ANTPOT.27 AL / Study of elastic scattering of \'ANTPOT.16O\' by \'ANTPOT.27 AL\'
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Eletrodesintegração do 232Th / Electro disintegration of 232ThLunardi, Leda Maria 05 December 1979 (has links)
Apresentamos nesse trabalho as medidas de seção de choque absoluta de eletrodesintegração e da taxa de produção da fotodesintegração para a reação 232Th(e,n) 231Th. A análise dos resultados de eletrodesintegração foi realizada pelo método dos fótons com a finalidade de determinar as multipolaridades das transições nucleares envolvidas nessa reação. As medidas foram realizadas no Laboratório do Acelerador Linear do Instituto de Física da USP, tendo se estendido de 7,5 a 26 MeV no caso das medidas de eletrodesintegração e de 20 a 25 MeV no caso das de fotodesintegração. Essas medidas foram feitas para testar a compatibilidade de nossas medidas com as realizadas com o uso de fótons monocromáticos, utilizadas na análise dos resultados de eletrodesintegração. Mostramos que a eletrodesintegração por emissão de um nêutron no tório se processa exclusivamente através de transições de dipolo elétrico. Nossos dados excluem uma contribuição das transições de quadrupolo elétrico maior do que 0,7% da intensidade das transições de dipolo elétrico. A nossa sugestão sobre o decaimento da ressonância isoescalar de quadrupolo elétrico é que este deve se processar preferencialmente pelo canal de fissão, comportamento similar ao do 238U. / The results of the absolute electro disintegration cross section as well the photodisintegration yield of the reaction 232Th(e,n) 231Th, are reported. We used the virtual photon formalism in the analysis of the electro disintegration data in order to establish the multipolarities of the nuclear transitions involved in the reaction. The measurements have been performed using the electron beam of the Linear Accelerator of the IFUSP, ranging from 7,5 to 26 MeV for the electro disintegration and from 20 to 25 MeV for the photodisintegration data. The photodisintegration yield has been measured to check the agreement between our data and those obtained with monochromatic photons, which are used in the analysis of the electro disintegration data. We show that electro disintegration by one neutron emission in thorium can be explained by a E1 process. Our data set up an upper limit to the E2 contribution of 0,7% of the E1 strength. We suggest that the isoescalar giant electric quadrupole resonance (GQR) decays dominantly through the fission channel, as in the 238U case.
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Estudo dos movimentos atômicos do t-Butanol do Espalhamento de nêutrons lentos / Study of the atomic motions of the slow neutron scattering t-ButanolAmaral, Lia Queiroz do 30 November 1972 (has links)
Estudo dos movimentos atômicos do t-Butanol do Espalhamento de nêutrons lentos / Study of the atomic motions of the slow neutron scattering t-Butanol
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Medidas do efeito de reorientação nos núcleos de 122Te, 128Te e 136Ba / Effect Measures Reorientation Cores 122Te, 128Te 136BaBechara, Maria Jose 21 September 1979 (has links)
Este trabalho apresenta medidas do efeito de reorientação nos núcleos de \'ANTPOT. 122 Te\', \'ANTPOT. 128 Te\' e \'ANTPOT. 136 Ba\'. O método utilizado é o do espalhamento elástico e inelástico de várias partículas carregadas (\'ANTPOT. 4 He\', \'ANTPOT. 14 N\', \'ANTPOT 16 O\' e \'ANTPOT. 18 O\'). As partículas espalhadas foram detectadas em ângulos traseiros por detectores de estado sólido de alta resolução. A comparação das probabilidades experimentais de excitação do primeiro estado \'2 POT. +\' com aquelas calculadas na aproximação semi-clássica de múltipla excitação Coulombiana possibilitou, para cada núcleo; uma determinação dos valores da probabilidade reduzida B(E2; \'O POT. +\'\'SETA\'\'2 POT. +\') e do momento de quadrupolo estático \'Q IND. 2 POT. +\' do primeiro estado excitado. São discutidas as limitações do método adotado, e os resultados obtidos são comparados com os de outros autores. Faz-se também uma comparação dos valores de B(E2; \'O POT. +\'\'SETA\'\'2 POT. +\') e \'Q IND. 2 POT. +\' previstos por modelos nucleares com os determinados experimentalmente. / Measurements of the reorientation effect in Coulomb excitation were carried out in 122 Te, 128 Te e 136 Ba. The experimental method adopted is the elastic and inelastic backscattering of several projectiles (4He, 14N, 16O and 18O). The scattered particles were detected by high resolution solid state detectors. The determination of the static quadrupole moment for the 1st. 2+ excited state, Q2+ and of the reduced transition probability B(E2; O+ 2+) was accomplished by comparing the measured probabilities of excitation with calculations based on the semi-classical theory for multiple Coulomb excitation. The limitations of the method are discussed and the results obtained are compared with existing data from other authors. Calculated values for B(E2; O+ 2+) and Q2+ predicted by nuclear models are compared with experiment.
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Estados de spin elevado em \'ANTPOT.130 La. / High spin states in \'La130\'.Rizzutto, Marcia de Almeida 27 October 1989 (has links)
Estados de spin elevado do núcleo duplamente ímpar ANTPOT.130 La foram estudados através de técnicas de espectroscopia gama em linha utilizando reações do tipo fusão-evaporação. Os raios gama de ANTPOT.130 La foram inicialmente identificados pelo método de reações cruzadas: ANTPOT.121 Sb (ANTPOT.12 C, 3n) ANTPOT.130 La e ANTPOT.124 Te (ANTPOT.10 B, 4n) ANTPOT.130 La. Foram realizadas medidas de função de excitação, distribuição angular e coincidência --t para a reação ANTPOT.121 Sb (ANTPOT.12 C, 3n) ANTPOT.130 La com energia de feixe de 54 MeV. Duas bandas rotacionais foram observadas com configurações h IND.11/2 g IND. 7/2 e h IND.11/2 g IND. 11/2 onde a segunda banda mostra um pequeno valor de signature splitting ( 50 KeV) que pode indicar uma forma ligeiramente triaxial. Os resultados experimentais serão comparados com os núcleos vizinhos ímpares e ímpar-ímpar e também interpretados segundo modelos de Roto mais duas quasipartículas e Cranked Shell Model. / High-spin states in the doubly odd nucleus ANTPOT.130 La have been studied using in-beam spectroscopy techinques with fusion evaporation reactions. The ganma rays of ANTPOT.130 La were initially identified by cross-beam reactions ANTPOT.121 Sb (ANTPOT.12 C, 3n) ANTPOT.130 La and ANTPOT.124 Te (ANTPOT.10 B, 4n) ANTPOT.130 La. Excitation functions, angular distributions and --t coincidences were measured using the reaction ANTPOT.121 Sb (ANTPOT.12 C, 3n) ANTPOT.130 La at E IND.BEAM = 54 MeV. Two rotational bands were observed with the configuration h IND.11/2 g IND. 7/2 and h IND.11/2 g IND. 11/2. The second band shows a small signature splitting of 50 KeV which could indicate a slightly triaxial shape. The results will be compared with the framework of Triaxial Rotor plus Two-Quasiparticule Model as well as Cranked Shell Model.
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Mecanismos de reação em 20Ne (d,p) 21Ne / Reaction mechanisms in 20Ne (d,p) 21NeAcquadro Quacchia, Juan Carlos 18 April 1973 (has links)
É apresentada uma avaliação das contribuições relativas dos mecanismos de interação direta e de núcleo composto, descritos pelos formalismos de DWBA e Hauser-Feshbach, respectivamente, para a reação ANTPOT. 20 Ne (d,p) ANTPOT. 21 Ne (1º estado excitado). Esta avaliação é feita mediante a determinação experimental dos parâmetros de população, isto é, a população relativa de sub-estados magnéticos, do 1º estado excitado do ANTPOT. 21 Ne, na faixa de energias do deuteron entre 1.0 e 3.0 MeV. Os parâmetros de população dos sub-estados |M IND. 1| = 1/2 foram obtidos de aproximadamente 60 correlações angulares próton-gama, utilizando o Método II de Litherland e Ferguson (Li 61). Valores médios destes parâmetros, foram calculados em quatro intervalos superpostos de energia, de ~800 keV cada um. A avaliação das contribuições relativas dos dois mecanismos foi feita seguindo o método sugerido por Goldfarb e Wong (Go 66). Por outro lado, as contribuições dos dois mecanismos podem, também, ser avaliadas, a partir de dados de secção de choque. Para este propósito, curvas teóricas de secção de choque, preditas pelos formalismos de DWBA e Hauser-Feshbach, foram ajustadas a valores médios de distribuições angulares de prótons da reação ANTPOT. 20 Ne (d, p IND. 1) ANTPOT. 21 Ne, calculados nos mesmos quatro intervalos. Os resultados obtidos por estes dois métodos concordam na faixa de energia entre 1.5 e 3.0 MeV. Na faixa entre 1.0 e 1.5 MeV, o método dos parâmetros de população, mostra, para a razão das populações dos sub-estados |M IND. 1| = 3/2 e |M IND 1| = 1/2, um valor maior que o dobro do valor obtido, para esta mesma razão, mediante a análise da secção de choque. Esta discordância foi interpretada, como sendo devida à existência de uma ressonância no sistema ANTPOT. 20 Ne + d. É mostrado que a análise feita com os parâmetros de população pode indicar o spin dessa ressonância. / The present work is an evaluation of the relative contributions of the direct and compound nucleus mechanisms, described by the DWBA and Hauser-Feshbach formalisms, respectively, for the 20Ne(d,p) 21Ne reaction leading to the first excited state of 21Ne. This evaluation is done through the experimental determination of the population parameters, i.e., the relative population of magnetic substates, for the first excited state of 21Ne, in the incident deuteron energy range of 1.0 to 3.0 MeV. The population parameters of the |M1| = 1/2 substates were obtained from each of approximately 60 proton-gamma angular correlations, measured using the Method II of Litherland and Ferguson (Li 61), Average values of these parameters were calculated in four overlapping energy intervals of - 800 keV each. The relative contributions of the two mechanisms was evaluated following the method suggested by Goldfarb and Wong (Go 66). On the other hand the relative contributions of the two mechanisms can also be evaluated from data on cross-sections. For this purpose, theoretical cross-sections, predicted by the DWBA and Hauser-Feshbach formalisms, were adjusted to fit the average proton angular distributions from the 20Ne(d,p) 21Ne reaction, calculated in the same four intervals.
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