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Foram medidas as energias de 21 transições gama dos nuclídeos 57Co,60Co, 133Ba, 137Cs e 192Ir, utilizando um detetor HPGe de 75cm3. Na análise dos dados foi aplicado o procedimento de auto calibração,baseado no Método dos Mínimos Quadrados, no qual as informações experimentais e dos dados de entrada são incluídas em um único passo. Como conseqüência do procedimento estatístico adotado, foi possível atualizar os valores de 309 outras transições gama não medidas, mas covariantes com aquelas que foram medidas, bem como de sua matriz de covariância. Assim, certas transições tiveram redução de variâncias superiores a 80% em relação aos dados então disponíveis na bibliografia e 50% em relação aos dados reanalisados considerando toda a matriz de covariância. / We measured 21 gamma-ray energies from 57Co, 60Co, 133Ba, 137Cs and 192Ir decay, with a 75 cm3 HPGe detector. The data analysis was performed usin a self calibration procedure, based on the Least Square Method, where experimental and input data are included in a single step. As result of this statistical procedure, 309 other gamma-ray energies not measured, but covariant with the measured ones, as well the covariance matrix were updated. Some transitions got a variance reduction over than 80% when compared with the bibliography, and of 50% when compared with the reanalyzed data that consider all the covariance matrix.

Thesis (M. Phil.)--Chinese University of Hong Kong. / Bibliography: l. 58.

Os espectros vibracionais Raman e infravermelho de compostos de ftalimidas, tais como, N-h-ftalimida, N-d-ftalimida, ftalimida de potássio, N-h-tetracloroftalimida, N-d-tetracloroftalimida, tetra¬cloroftalimida de potássio, N-h-tetrabromoftalimida, N-d-tetrabromoftalimida, tetrabromoftalimida de potássio, N-h-tetraiodoftalimida, N-d-tetraiodoftalimida e tetraiodoftalimida de potássio, foram registrados, respectivamente, na região de frequência de 4000 a 50 cm-1 e de 4000 a 160 cm-1 para amostras policristalinas. As bandas observadas foram atribuídas, tentativamente, considerando-se a estrutura molecular C2v comparando com os espectros vibracionais Raman e infravermelho do anidrido ftálico, anidrido tetracloroftálico, anidrido tetrabromoftálico e anidrido tetraiodoftálico. As moléculas de imidas e anidridos são isoeletrônicas. As análises de coordenadas normais dos anidridos ftálicos e ftalimidas foram realizadas considerando-se um campo de força molecular do tipo de valência generalizado. Os cálculos numéricos foram efetuados usando um conjunto de programas de computação em linguagem FORTRAN IV, para as vibrações normais no plano e fora do plano . As constantes de força definidas foram ajustadas pelos cálculos de quadrados mínimos, para reproduzir as frequências fundamentais observadas nos espectros vibracionais. As distribuições de energia potencial para coordenadas de simetria foram também calculadas para confirmar as atribuições feitas. Com base nas frequências observadas e nas intensidades relativas dos espectros Raman e infravermelho e nos cálculos de constantes de força e de distribuições de energia potencial, foram discutidas as vibrações normais e fundamentais das moléculas de ftalimidas e anidridos ftálicos e a natureza das ligações químicas nos sistemas de O=C-N-C=O e o=c-o-c=o e de anel benzênico. Os deslocamentos das frequências vibracionais e os desdobramentos das bandas observadas das vibrações de estiramento C=O, N-H e N-D foram explicados usando os termos de migração dos elétrons nos sistemas π, ponte de hidrogênio intramolecular e intermolecular, e ressonância de Fermi. Aplicando as regras de seleção vibracional e exclusão mútua Raman-infravermelho para as estruturas moleculares e cristalinas, as bandas observadas foram também discutidas considerando-se as funções potenciais moleculares. / The vibrational Raman and infrared spectra of the compounds of phthalimides, such as N-h-phthalimide, N-d-phthalimide, potassium phthalimide, N-h-tetrachlorophthalimide, N-d-tetrachlorophthalimide, potassium tetrachlorophthalimide, N-h-tetrabromophthalimide, N-d-tetrabromophthalimide, potassium tetrabromophthalimide, N-h-tetraiodophthalimide, N-d-tetraiodophthalimide and potassium tetraiodophthal¬imide, have been measured, respectively, in the frequency region from 4000 to 50 cm-1 and from 4000 to 160 cm-1 , for the polycrystalline samples. The observed bands have been assigned, tentatively, considering a molecular structure C2v and comparing with the vibrational Raman and infrared spectra of phthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic anhydride and tetraiodophthalic anhydride. The molecules of imides and anhydrides are isoelectronic. The normal coordinate analyses of phthalic anhydrides and phthalímídes have been carried out consideríng a molecular force field of the general valence type. The numerical calculations have been made usíng a set of computer programs written in FORTRAN IV, to the lnplane and out-of-plane normal vibrations. The defíned force constants have been adjusted by the least squares calculatíons to reproduce the observed fundamental frequencies of the vibrational spectra. The potentíal energy distributions for the symmetry coordinates have also been calculated to confirm the proposed assignments. The normal and fundamental vibrations of the molecules of phthalímides and phthalic anhydrides and the nature of chemícal bond of the O=C-N-C=O and O=C-O-C=O systems and of the benzene ríng have been discussed on the basis of the observed frequencies and relatíve intensities of the. Raman and infrared spectra and of the calculated force constants and potential energy distributions. The vibrational frequency shifts and observed band separations of the C=O, N-H and N-D stretching vibrations have been explained using the terms of π electron migration, intramolecular and intermolecular hydrogem bond and Fermi resonance. Applying the vibrational selection rules and the infraredRaman mutual exclusion rules to the molecular and crystal structures, the observed bands have also been discussed considering the molecular potential functions.

Two nonlinear optical experiments are presented in which the third-order electronic susceptibility of molecules is used to generate Raman signals. The first one uses a single 532 nm beam from a Nd:YAG laser to produce Stimulated Raman Scattering in benzene and deuterated benzene. With a simple experimental set-up, stimulated emission involving CC and CH (CD) stretching modes from both C���H��� and C���D��� can be visually witnessed. Collinear and conical stimulated Raman beams are observed and explained. Measuring the wavelengths of the coherent beams with a meter stick and a grating permits the calculation of CC and CH force constants in benzene. This experiment has been developed as a lab in graduate and undergraduate courses and has been submitted to J. Chem. Ed. for publication. The second experiment uses a high resolution Coherent Anti-Stokes spectrometer to investigate the v��� vibrational mode of the CD��� radical produced by photolysis of CD���I. Calibrated spectra are obtained at much higher resolution than in an earlier published study and efforts are described to improve the range of data and to reconcile differences between the spectra. Modeling of the spectra leads to a "best fit" set of vibration-rotation parameters for CD��� but a completely satisfactory fit of both high and low resolution spectra was not achieved. / Graduation date: 2003

Graduation date 1997

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