A very faint spectroscopic quasar survey was undertaken in order to define the statistical behavior of the low luminosity portion of the quasar population at high redshift and to search for evidence of a decline in space density. Both slitless and multi-aperture spectroscopic observations were obtained for approximately 750 objects with B magnitudes in the range 20 < B < 24. The total number of emission line candidates found was ~ 50 and there are 5 excellent quasar candidates, 3 very probably at high redshift. In addition to the quasar candidates a number of emission line galaxies have been identified. / Graduate

In this thesis I have given an account of the work carried out by me on the measurement of the spectra and decay times of a few selected organic phosphors under ultraviolet and ionising radiation. The purpose of the investigation has been to attempt to throw more light on the mechanism by which energy migrates within the crystalline lattice. A general introduction is given to the process of fluorescence and the various proposed theories by which the excitation energy, which eventually appears as fluorescence light, is able to move about in the crystalline lattice. Preface, p. 1.

The intensity of optical absorption, near the absorption edge in germanium, is examined as a function of strain applied to the lattice at 90 °K. The results are interpreted in terms of the change of the band structure of the lattice with applied strain. The absorption edge in unstrained germanium shows a single sharp peak due to exciton formation, whereas the edge in the strained specimens shows two exciton peaks. The peak positions vary linearly with both compressional and tensional strain up to the maximum strains applied (0.1% deformation). The exciton binding energies in the strained germanium lattice, calculated within the effective mass approximation, are approximately equal and independent of the magnitude of the strain. The separation of the peaks gives for the shear deformation potentials, the values |b| = (2.7 ± 0.3)eV/unit <100> shear and |d| = (4.7 ± 0.5)eV/unit <111> shear. The positions of the peaks give the shift of the energy gap as - (10.3 ± 1) eV/unit dilatation. Lattice imperfections are found to have no effect on the interpretation of the results. The broad absorption edge observed in evaporated films of germanium is accounted for in terms of internal strains. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Time-resolved spectrographic techniques were used to obtain the profiles of A II lines emitted from a laboratory plasma. For the dense, low-temperature plasma studied, most of the broadening of the observed lines results from interactions of the emitter with free charges in the surrounding plasma. The plasma was created by discharging a previously- charged lumped-parameter delay line through a specially- constructed vessel containing an argon-hydrogen mixture. By means of a rotating-mirror shutter, light from the discharge was admitted to the spectrograph during a time interval when the intensity of the A II lines was constant to within about 10%. This time interval was chosen after monitoring the time dependence of the intensity of several A II lines with a monochromator-photomultiplier combination. A calibration spectrum was also obtained with a seven-step neutral density wedge in order to determine the response of the photographic emulsion. Of the twenty-four measureable A II lines recorded, fourteen yielded profiles which could be treated by a Voigt analysis. In this way the profiles could be corrected for the effects of instrumental and Doppler broadening. The electron number density was determined from the widths of the lines in multiplet 6 of the A II spectrum, previously measured by other workers. The results indicate considerable disagreement with the original theory of line broadening as developed by Griem and his co-workers. The half-widths of the lines reported here are up to 4.0 times wider than predicted theoretically. The line shapes appear to be Voigt functions, rather than the predicted Lorentzian profiles. The measurements are in good agreement with those of other workers, where comparisons could be made. Measurements of some of the lines reported here do not appear to have been published elsewhere. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An axial asymmetry about, the direction of motion of Li⁵ has been seen in the breakup of the ground state of this nucleus as an intermediate state in the reaction Li⁶(He³,pα)He⁴. The total cross section for this process was found to be a few hundred millibarns, an order of magnitude greater than predicted by a statistical model calculation, and the asymmetry amounts to a factor of 2.0 ± 0.3 in the double, differential cross section. It is shown that this asymmetry in the secondary decay of the sequential breakup process can arise from the memory retained by the intermediate state of its structure during the primary reaction, in which a neutron is transferred from Li⁶ to He³. It was found that the strength of the asymmetry is sharply dependent upon the duration of the final state interaction. This confirms the proposed interpretation and suggests that further data could lead to useful information regarding correlation of the p-shell nucleons in the Li⁶ ground state. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

[No abstract available] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

[No abstract available] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Infrared spectra of and H₂O and D₂O trapped in solid argon, krypton and nitrogen have been obtained at 4°K. In addition, spectra have been recorded of D₂O in carbon tetrachloride and ammonia matrices at 77°K, and of a dilute solution of D₂O in carbon tetrachloride at 25°C. Dilution studies involving changing the matrix to water ratio from 50 to 500 have been carried out with D₂O in argon at 4°K. Changes in the spectra of D₂O and H₂O in argon, krypton and nitrogen matrices during warm-up have been observed. The dilution and warm-up studies have made it possible to assign certain peaks to monomer, low polymer and higher polymers. The complex spectra of H₂O and D₂O in argon, krypton and nitrogen at liquid helium temperatures are discussed, and previous simple explanations involving molecular association, rotation and multiple trapping sites advanced by other workers are shown to be inadequate. Consideration is given to the isotope effect and interactions with the matrix in an attempt to account for the observed spectra. / Science, Faculty of / Chemistry, Department of / Graduate

The atomic and ionic spectra of lead have been photographed in the region between 350 A and 7680 A, using a three meter normal incidence vacuum grating spectrograph, and a Hilger large quartz-glass prism spectrograph. Spectroscopic sources used throughout this region were the electrodeless discharge, and the condensed spark in helium. Approximately 4075 lead lines were measured, and of these, 1006 have been classified in the spectra of Pb I, Pb II, Pb III, and Pb IV. The Pb IV analysis has been extended: relative energies have been assigned to eight even and two odd levels arising from the 5d¹ºns, np, nd and ng configurations, and tentative values given to several levels from the 6s7s and 6s6d configurations of the 5d⁹ core. The core-polarization theory has been applied to the observed 5g - nh transitions of Pb IV, giving a value for the ionization potential of 341438 cm⁻¹. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Measurements have been made of the integrated absorption coefficients of the three fundamental vibration-rotation bands of sulfur dioxide vapor. In contrast to previously reported values of these intensities, the molecular dipole moment calculated from them differs widely from the static dipole moment determined by other methods. The magnitudes of the bond moment derivatives are not in agreement with simple molecular models, indicating that infrared intensities are sensitive to the details of the electrical charge redistribution accompanying molecular distortions. The possible role of unshared electrons is discussed. Observations on the shapes, frequencies, bandwidths, and intensities of some absorption bands of sulfur dioxide and carbon disulfide in condensed phases are reported and discussed in terms of the information they may give on intermolecular interactions. / Science, Faculty of / Physics and Astronomy, Department of / Graduate