The continuous spectrum of gamma radiation which accompanies the capture of orbital electrons has been recently calculated independently by Glauber and Martin (1954), and by Hess (1955). Both calculations take into account the influence of the nuclear charge on the wave functions but otherwise involve different methods and approximations, the conclusions being also quite different: the intensity of the gamma radiation is an order of magnitude lower according to Hess than according to Glauber and Martin. The purpose of the calculations presented in this thesis has been to settle this disagreement and to explain its origin. To this effect the high energy part of the gamma spectrum, which is almost entirely determined by the contributions of the capture of the 1s and 2s electrons, has been computed for the case of A³⁷ for which experimental data are available. In view of the low nuclear charge of A³⁷ (z = 18), the non-relativistic Coulomb wave functions could be used, and, apart from neglecting screening effects, the calculations are exact although partly numerical. In particular, the retardation effects which were neglected by Glauber and Martin have rigorously been taken into account. The conclusions are: first, approximations used by Hess were partly inconsistent, although the method was in principle correct; second, taking into account retardation effects results in a gamma spectrum whose intensity amounts to 0.81 of the intensity obtained by Glauber and Martin at 135 Kev, and to 0.24 at 675 KeV (the gamma spectrum limit being 816 KeV). The gamma spectrum of A³⁷ determined by Lindqvist and Wu (1955) seems to agree quite well with Glauber and Martin's result. However, Lindqvist and Wu measured only relative intensities and had to apply many instrumental corrections so that it is not yet clear whether the measured spectrum would not agree as well with the spectrum computed in this thesis. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Spectroscopic measurements were made on a long-lived Argon plasma to determine the electron temperature and density and to examine the validity of the thermal equilibrium relations used. The derived results when compared with Griem's equilibrium criteria indicate that a complete thermal equilibrium was not established. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A conversion electron and low energy gamma-ray spectrometer has been developed using a silicon lithium-drifted semiconductor detector. The spectrometer has a resolution of 2 Kev for 100 Kev electrons and photons under optimum conditions. The energies of these electrons and gamma-rays can be estimated to ±.1 Kev, and their intensities to within ±6% with the standard sources available. The electron capture decay of ¹⁵³Gd → ¹⁵³Eu was investigated using this spectrometer. The branching capture ratios to the 172.9 Kev, 103.2 Kev, 97.4 Kev, and 0 Kev levels of ¹⁵³Eu were found to be 11%, 39%, 39% and 11%, respectively. Possible Jπ values of ⁵ ̸₂ + or ³ ̸₂ + for the 172.9 Kev level, ⁵ ̸₂ + or ³ ̸₂ + for the 103.2 Kev level, and ³ ̸₂ -, ⁵ ̸₂ -, or ⁷ ̸₂ - for the 97.4 Kev level have been assigned. These values are in agreement with those found by other investigators. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This describes a study of some unusual features of the hydrated electron, [symbol omitted] in particular the kinetics of its decay during a period of non-homogeneity lasting tens of nanoseconds, the formation and photodissociation of a hydrated dielectron species [symbol omitted], and the photoexcitation of [symbol omitted]. Nanosecond pulse radiolysis (p.r.) studies on the kinetic behaviour of [symbol omitted](> 10⁻⁴ M) in pure deaerated water revealed a complicated interplay of mechanisms for the first half life ∼110 nsec. This is partly attributable to an initial non-homogeneity in the distribution of reacting species within the system, because the spurs are essentially isolated for tens of nanoseconds. Calculations based on a qualitative model revealed that the times necessary for spur-overlap through diffusion (during which > 40% [symbol omitted] were lost to reaction) were in agreement with experimental observations. However the anomalous trends in κ, a rate parameter describing [formula omitted] within this period, led to the subsequent discovery of a process by which [symbol omitted] were formed after the electron pulse. The use of selective ion and radical scavengers strongly implied that the increase in [symbol omitted] occurred via another radiolytic product, XB. Three plausible mechanisms have been outlined in which XB is (e_ ) [formulae omitted]. XB undoubtedly affects the values of κ but it is not possible at this time to discard the notion of microscopic non-homogeneity within the spur itself as the trends in κ might suggest. Four conclusions are drawn; (i) in some p.r. studies we may not calculate meaningful second order rate constants with concentrations evaluated from optical density data, (ii) the "instantaneous" yield of [symbol omitted] seen through nsec p.r. is higher than that established through μsec p.r. or steady-state techniques because of the rapid initial loss of [symbol omitted] (iii) but the total [symbol omitted] yield will be less since the latter techniques cannot distinguish the source of [symbol omitted]. (iv) there is a critical need for a nanosecond p.r. yield of [symbol omitted] to establish the true primary yield, [symbol omitted]. Some microsecond flash photolysis (f.p.) experiments were performed on hydrogen saturated alkaline solutions. Hydrated electrons were produced following the ultra-violet photolysis of OH⁻ and reacted bimolecularly to give a species which on subsequent infra-red flash photolysis regenerated [symbol omitted]. This species is postulated to be a hydrated electron dimer [formula omitted] the spin state of which is unspecified The remaining purpose of this work was to photoexcite [symbol omitted]. The nature of the excited state of [symbol omitted] and the origin of the optical absorption band is still open to speculation although Jortner and others have performed calculations in which the transition at λmax is assigned to a 2p + 1s excitation. The photolysis of [symbol omitted] was attempted through both p.r. and f.p. techniques, neither of which yielded any conclusive information because of the presence of XB or [symbol omitted] in the system. / Science, Faculty of / Chemistry, Department of / Graduate

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Thesis (M.Sc.)--York University, 2007. Graduate Programme in Physics. / Typescript. Includes bibliographical references (leaves 137-141). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR29542