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.

University of Macau / Faculty of Science and Technology / Department of Computer and Information Science

M.Sc. (Chemistry) / The aim of this investigation was to study, and if possible, to correct curvature of calibration lines when solutions are analysed by X-ray fluorescence spectrometry. The two main metallic elements used for this purpose were copper and cadmium, with a short study of nickel, cobalt and iron. The concentration ranges investigated were from 0,01 % (rn/rn) to 10 % (rn/rn) in the solution sample ...

Double perturbation theory is applied to the problem of measuring the molecular dipole moment of a linear or symmetric top molecule in the presence of a single quadrupolar nucleus. A computer program is developed and a new value for the dipole moment of methyl iodide is reported. / Science, Faculty of / Chemistry, Department of / Graduate

A complete system for the detection and recording of astronomical spectra has been constructed using an image isocon (E.E.V. P850) television tube as detector. The detector will accomodate two spectra 80 millimeters in length and has the spectral response of an S-20 photocathode. Recording is onto IBM-compatible magnetic tape via an on-line computer. The user is also provided with a real time display of the spectra on an oscilloscope via the computer. A description of the video signal circuits is given. Schematic diagrams of the control unit constructed by the author and the modified camera are shown. A method of determining the modulation transfer function of the detector, based on the Fourier analysis of the signal output for a known signal input, is described. The MTF as a function of light level, exposure time, and target temperature is investigated. It can be seen that the best MTF for a particular exposure time occurs at the lowest target temperature. The MTF far exceeds that predicted as the maximum by direct application of the analysis of Krittman (1962). It is assumed that the Krittman analysis can not be applied to the P850 image isocon with its large target mesh-to-target spacing and thin target. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Detailed measurements were made of the profiles of the lines HeI 4471 and 4922 Å in a pulsed arc plasma, for electron densities in the range 3 x l0(16) to l0(17) cm(-3) and at a temperature of 4.5 eV. Photoelectric detection was employed in a rapid scan spectrometer. The relative intensities agreed well with the computed values, but the component peaks for each line were closer together. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Stimulated Raman scattering (SRS) has been studied experimentally in a CO₂ laser plasma interaction. A N₂ gas jet target was irradiated with CO₂ laser light (wavelength, ⋋ = 10.6 µm and frequency, ѡ₀) at intensities up to 10¹⁴ Wcm⁻². SRS occurs at intensities greater than 3 x 10¹³ Wcm⁻², which is fair agreement with threshold predictions for a plasma with an electron temperature of 300eV and a density scale length of 300µm. After this intensity is reached, the plasma waves grow exponentially in time with a growth rate of 6 x 10⁻³ѡ₀. This was measured with ps resolution ruby laser Thomson scattering. Spatial growth was also observed. Scattered infrared light at 2⋋ was found. Weak IR light in a broad band near 15µm was also found. The saturated plasma wave level and the number of hot electrons at 150 keV are well correlated, which indicates that trapping is responsible for the electrons. However, trapping is not responsible for the saturation of the instability. Frequency resolved Thomson scattering revealed that ion acoustic waves start at the peak of the SRS fluctuations. Once the ion acoustic waves grow to a large amplitude, SRS is quenched and does not reappear. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The excitation function for the reaction ⁵⁶F(p,y)⁵⁷Co has been measured from 1200 - 3000 KeV proton energy using enriched ⁵⁶Fe targets. Gamma-ray spectra were measured using Ge(Li) and NaI(T£) detectors. The resonance strength, 10^, has been determined for the studied resonances. Gamma-ray angular distributions were measured using NaI(T£) detectors. In the energy region between 1240 and 1272 KeV, the gamma-ray angular distributions were measured using the Ge(Li) detector. Gamma-ray angular distributions have been measured for resonances corresponding to excitation energies in ⁵⁷Co of 7253, 7267, 7272, 7598, 7622, 7641, 7647, 7925, 8192 and 8450 KeV. The-branching ratios, spins and parities of the resonance levels as well as some of the low-lying states in ⁵⁷Co have been established. The reaction Q-value derived from these measurements is Q = 6027 ± 3 KeV. From the gamma-ray spectra and angular distributions which have been studied the levels at 7253, 7267 and 7272 KeV excitation in ⁵⁷Co are identified as the split analogue of the T = 5/2 corresponding to the first bound state in the parent nucleus ⁵⁷Fe at 14 KeV. The group of levels at 7622, 7641 and 7647 KeV excitation in ⁵⁷Co are believed to form the split analogue of the 367 KeV bound state in 57Fe. The level at 8450 KeV excitation is tentatively identified as the isobaric analogue state of T = 5/2 corresponding to the 1196 KeV bound state in ⁵⁷Fe. The absence of the isobaric analogue resonance corresponding to the ground state in ⁵⁷Fe is discussed as a result of the present study. A coulomb displacement energy for ⁵⁷Co - ⁵⁷Fe of 8876 ± 6 KeV is deduced from these measurements. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A comparative study has been made of Penning ionization (He*(2¹S) and He*(2³S)) and photoionization (He(584 Å)) of twenty-three atoms and molecules (Ar, Kr, Xe, H₂, HD, D₂, N₂, CO, NO, 0₂, C0₂, COS, CS₂, N₂0, S0₂, N0₂, NH₃, CH₃CI, CH₃Br, CH₃I, CH₄, C₂H₄ , C₂H₂) employing the techniques of high resolution electron spectroscopy. Electron spectra from mixed rare gas systems, at higher pressures, have also been examined and interpreted on the basis of fast neutral-neutral interactions. / Science, Faculty of / Chemistry, Department of / Graduate

Energy loss spectra of 2.5 keV electrons, scattered by molecular targets through small angles, have been studied in the regions of the respective carbon, nitrogen, oxygen and fluorine K-edges and the sulfur LII,III edges. Electron energy loss spectra for diatomic, triatomic and polyatomic molecules have been studied. Discrete excitations have been interpreted in terms of the promotion of the respective K-shell electron to unfilled valence molecular orbitals and Rydberg orbitals. Most spectra show considerable structure above the respective K-edge, in addition to the normal K-continuum. This structure represents the simultaneous transitions of a K-shell and valence shell electrons (i.e. shake-up and shake-off events following the creation of an inner hole). In the case of molecular nitrogen and carbon monoxide, a simple core model was shown to provide an accurate description for the K-shell excited molecule. On the basis of this model, excitation and ionization energies for some exotic chemical species have been predicted from the relative energies observed in the K-shell energy loss spectra of a number of molecules. The agreement between the estimated (core analogy) and observed K-shell excitation energies for larger molecules is less satisfactory, possibly because of the large changes in molecular geometry which occur as a result of an election promotion. Finally, the carbon K-shell energy loss spectra of carbon disulfide, carbonyl sulfide and carbon tetraf1uoride show features which are possibly associated with the existence of an effective potential barrier in these molecules. / Science, Faculty of / Chemistry, Department of / Graduate