Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3872. Adviser: Paul G. Kwiat. Includes bibliographical references (leaves 109-115) Available on microfilm from Pro Quest Information and Learning.

Thesis (M.S.) in Civil Engineering--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 175-177).

PART I: The Fabry-Perot interferometer is generally used in transmission. It is described how it can be modified so that the fringes can be used in reflection. The general theory of the reflection fringes is considered. It is shown that the interferometer used in reflection is about 30 times faster in light speed than one used intransmission. It is shown how the technique can beadopted to the measurement of wavelengths and to the evaluation of the line-widths of lines from weak sources. PART II: Hyperfine structure examinations are carried out over the range 6000 to 3700 in the arc spectrum of bromine and over the range 5500 to 3900 in the spark spectrum of bromine. Twenty-one lines in the arc spectrum of bromine are examined. Eighteen classified and twenty unclassified lines in Br II spectrum are measured for the first time and hyperfine structure term interval factors are derived for fourteen terms in thespark spectrum of bromine. The theory of the hyperfine structure analysis is considered in brief. Both the arc and the spark spectra are obtained by employing a circulating system and a high frequency oscillator. The analysis of the lines fits well the term scheme. A few anomalies have been noted and have been accounted for, some of them being due to faulty interpretations of the lines by previous workers. Deviations from the interval rule occur in the arc spectrum of bromine and these are completely explained by the existence of an electrical quadrupole moment of nuclei for both the bromine isotopes. The coupling constants for the terms concerned are determined from the term values and using these, both the quadrupole moment and the magnetic moment of the bromine nucleus are evaluated.

Multiple-beam Interferometry has been applied to the study of the surface topography of natural and synthetic quartz crystals. It is shown that the principal habit faces (major rhombohedron R. minor rhombohedron r. and prism m) consist of a number or 'growth pyramids', which are produced by the spreading of multimolecular growth sheets In succession from several initiating centres. A description if given of the properties of these sheets (height, edge structure etc.) on the R faces, and of the vicinal faces constituting the sides of the growth pyramids. There are two respects in which the vicinal faces depart from the condition of being strictly plane. - They possess a cylindrical curvature with a radius of several metres and their inclination to the close-packed plane increases towards the summit of the growth pyramid. From the Interpretation of the results the mechanism of growth of the R faces is determined, and estimates are obtained of the mean distance of diffusion of adsorbed molecules and of the size of the theoretical two-dimensional nucleus. The general features of the minor rhombohedron faces are similar to those of the R faces. Differences arise due to the greater irregularity of the growth fronts of the r faces, and this is probably connected with their greater rate ofspreading. The topography of natural prism faces is briefly described, and the origin of the atriations on these faces. Two types of synthetic crystal have been studied; seeds with a thin layer (order of one wavelength) of synthetic growth, and crystals with a om. or more of synthetic growth. The observations on these crystals indicate that growth initially takes place from a large number of growth nuclei of the order of but that as growth proceeds, most of these nuclei becomes Inactive and ultimately growth takes place from relatively few dominant centres. Evidence is given for the existence of screw dislocations in quarts; and from the observations on natural and synthetic crystals it is concluded that fresh sheets are Initiated by screw dislocations, by the re-entrant angles associated with twinned faces and, possibly, by foreign particles.

The results of optical studies on some crystal surfaces - cleavage and etched, with special reference to diamonds are reported in the thesis. It is divided into four parts. In the part I, a brief historical review of the studies on crystal growth is given as a general introduction. The existing information on diamond is also described. All the experimental techniques used in the course of this work are given in part II. The techniques used were (1) Multiple beam interferometry (2) Phase contrast microscopy (3) Light profile microscopy (4) Optical goniometry in part III is given a description of the optical studies of cleavage surfaces of topaz, calcite, mica and diamonds type I and type II. Both the surfaces obtained on cleaving a crystal were examined and the counter parts were matched for comparison. In the case of topaz, calcite and mica the matching was exact within limits of interferometric measurements, where as in the case of diamonds there were marked differences. The cleavage surface of type I diamond is very rough compared to that of type II diamond which is a strong difference in the cleavage. In the case of one pair of type II diamond triangular depressions were noticed. An explanation for these is offered. In the last part the evolution of etch phenomena on natural octahedron faces, cleavage (111) face, polished dodecahedron faces and polished cube faces, produced by immersion in hot potassium nitrate in temperatures ranging from 500° to 700°C is reported. In the case of natural (111) faces the etching process though a continuous one, is divided into three stages. The first stage begins with preferential attack on any surface flaws and then develops into random distribution of small etch pits. The concentration of these pits is less within growth trigons than elsewhere. In the second stage relatively small number of etch pits grow steadily and devour their smaller members. The corners become rounded and flat bottomed pits are frequent. In this stage, growth trigons tend to become hexagonal in outline and this mechanism is unfolded. In the third stage the whole of the original face has been eaten away. Triangular pyramidal depression begins to grow deeper and ultimately striking block formation results. The pile of blocks has plane surfaces which are mainly (221), (212), (122) and less prominent (331), (313), (133) which tend to become (334) but then rounding sets in. In the case of etching of cleavage (111), polished dodecahedron and polished cube faces, the etch pits observed are triangular for (111), boat-shaped for (110) and square for (100). Some of these are evaluated and discussed. Appearance of strongly marked rectilinear pattern proves each of the diamond to have laminated structure.(111) face is crossed with lines parallel to (111) edges, the (110) face is filled with beautifully regular set of concentric hexagons with sides parallel to (111) edges and the cube face reveals an equally striking set of concentric rectangles filling most of the face. The etch patterns reveal a sectional history of the growth of diamond. The observations can be accounted for by postulating increased resistance to etching at the on-set (or end) of each layer. The proposed growth by sheet layers is in conformity with the failure to find growth spirals on natural octahedron diamond faces.

Part I. A number of modifications were made to the large spheroidal field B-spectrometer and a small lens spectrometer was attachedto it for 3-3 coincidence measurements. The method of ion ejection from a capillary tube for preparing thin sources was developed and used for making Ce144 sources. An attemptwas made to verify the existence of a 166 keV excited statein Pr 144 suggested by some investigators by observing the predicted Y-Y cascade, i.e. 33 keV Y-ray followed by a 133 keV Y-ray. No evidence of B-B coincidences between the K133 and L133 conversion lines was found. Part II. The trajectories of electrons in a spheroidal field were found by integrating the equations of motion using the electronic computer 'Mercury' of the University of London. The focusing properties of a B-spectrometer using this field were investigated and an attempt was made to find an analytical form for the field intensity which would describe the field in the large spectrometer.

The conditions of use of interference fringes for topographical measurement of metal surfaces are investigated. The optimum conditions of the factors which are involved in the formation of fringe systems in reflexion and which control the sharpness and contrast of the fringes are determined. The limits of resolution of the interference method are discussed with relation to the scale of the surface deformation structures of typical metal crystals. The mechanical twinning of suitably shaped single crystals of Bi, Sb and Sn is investigated and the interferometric measurements of the macroscopic shear of the specimens allows a full determination of the twinning elements involved. These goniometric measurements are pursued to the microscopic scale and thus attention is drawn to the shape of the initial region of twinning and its development; the observations being interpreted against the background of the elastic anisotropy of the metal crystals measurements are made upon the phenomenon of slip by way of the slip bands produced on crystals of Aluminium subject to shearing stress up to 1 kgm.mm-2. The commencement of the translation involved in the formation of surface steps is found to be very rapid but the bands subsequently developed by a more gradual process accompanied by movement of the lamellae between active slip bands; the small angles of tilt involved being measured by means of fringes. The measurements in conjunction with a dislocation model of slip yield quantitative data.

If we consider the general case of two intersecting spherical surfaces of different radii of curvature, then as each of the radii of curvature increases without limit along the line joining the centre of the corresponding sphere to a fixed point on the line of intersection, the two intersecting surfaces tend in the limit to two planes forming a wedge. If one of the radii of curvature increases without limit and the other remains constant, the first surface tends to a plane and we have the case of an interferometer consisting of a plane and a spherical surface. A lens-plate interferometer is a special case when the plane is tangential to the spherical surface. An arbitrary surface and a plane could be considered to be an extension of the previous simple case. If the two spherical surfaces are concentric, we have a spherically curved thin film of uniform thickness, a central section through which is identical with the section perpendicular to the axis of a cylindrically curved thin film. As the radii of curvature increase without limit, the interferometer tends to two planeparallel surfaces. By evaporating a highly reflecting semi transparent metallic film on Both components of these interferometers, multiple beam interference fringes are obtained. Their intensity distribution approaches a Fabry-Perot distribution with the result that there is extreme sharpness of the fringes. Localization arises from the difference in angles of emergence of the beams leaving the two sides of the interferometer. This depends on the difference in angles of incidence at the first and second surfaces of the interferometer. In the case of a wedge, for incident parallel light, the angles of incidence at the first and second surfaces are constant and their difference is equal to the wedge angle. The interferometer gap t varies along the wedge. It satisfies the linear relation t = y tan where y is the distance measured from the apex along one of the components. In the case of a lens-plate interferometer, a slight variation in the angle of incidence occurs along the curved surface. The interferometer gap t is related to y by the second order equation t2- 2Rt = y2. For cylindricallycurved thin films, the angles of incidence at bothsurfaces vary from nearly while theirdifference as well as the interferometer gap remain constant. Tolansky (1) applied and developed multiple bean interference to both the cases of a lens-plate and an arbitrary surface plate interferometers. The latter is case of Fizeau fringes. The present work deals with the theory of formation and properties of localized fringes obtained by cylindrically curved thin films. Their application to isotropic, uniaxial and biaxial media is considered in detail.

The work consists of optical and interferometric studies of growth, slip, and etch phenomena on diamond octahedral faces. For this study special experimental techniques have been developed. These comprise: (a) Thin film technique tor high magnification topographical studies. (b) Micro-flat for the study of rough surfaces. The study includes (1) Evaluation of inter-facial angles of growth hillocks and trigone, so familiar on diamond surfaces. This is carried out by means of multiple beam interferometry, the method competing with goniometry. A similar procedure is adopted to the etch pit. (2) Cylindrical curvature is discussed and values are obtained for both hillocks and vicinal faces. Trigons are similarly treated, but they are included in another study of a statistical nature (depth versus size). (3) A theory is developed to account for the existence of trigone. This is first presented as a speculation but is later supported by facts. (4) Slip has been substantiated to exist in diamond. This has been discovered and studied by means developed in this thesis. The slip plane has been identified as the (111) plane. An opacity has been observed (intimately connected with the slip) which has bean duly interpreted. (5) By artificially etching diamond at a much lower temperature than is usually adopted, etch pits have been observed to be spirally connected. The spirals are oriented in conformity with the crystal symmetry. The susceptibility of the shape and size of the etch pit to the etching temperature has been investigated, also the distribution of depth amongst the etch pits. (6) The temperature at which the diamond has formed is calculated, and a procedure to be adopted for the complete confirmation is outlined.

The work has been mainly concerned with the irregularities which are found in the electron images of emitting oxide cathodes. An electron emission microscope has been designed to produce pictures at magnifications of up to x 120. Electron pictures from oxide cathodes have been compared with the optical picture of the cathode surface and a correlation has been found to exist between the two types of picture from the same part of a cathode. This result is in contradiction to the findings of earlier investigators. In view of this new evidence of the correlation, the causes of irregularities in the emission picture have been reconsidered and a revised list of the possible causes has been given. In an attempt to produce a cathode which emits uniformly, a technique has been developed for coating the core of the cathode. The polished core is coated by evaporating the oxide on to it. The cathodes produced in this way had smooth surfaces and uniform emission pictures were obtained. The emission pictures did not remain uniform but altered in character during the life of the cathode. Experiments were performed to establish the reasons for the observed sequence of emission pictures. A theoretical explanation of the emission pictures hasbeen attempted using a semiconductor model for the oxide coating. An equation for the saturated emission current is derived for different forms of the semiconductor model and it is shown that all the models lead to an equation of the form [equation] where A, n and O are constants which depend on the model used. The emission from a metal coated with a semiconductor is considered and it is shown that with a model of the contact between the metal and the semiconductor which assumes space charge barriers, an explanation of the sequence of emission patterns is possible.