In this thesis detailed calculations are given showing the equivalence of Siegert's derivation of the nuclear resonance scattering formula, and Hu's derivation of the same formula. Although at first glance it appears that Hu has given a solution to the problem using an entirely different formalism, we have shown that no matter what the final expression for the resonance scattering cross section may be, it must be the same in the case of Siegert's calculation and that of Mng Hu, provided of course, that no more or less arbitrary approximations are introduced into the calculations. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Rayleigh Scattering from neutral nitrogen and argon at room temperature has been studied using a 12 megawatt Q-switched pulse ruby laser. The scattering angle was chosen to be 90 degrees from the incident beam. The relative differential scattering cross-section and the pressure dependence of the scattered signal of the scattering media were determined. Measurements of the absolute differential cross-section of nitrogen and argon were also obtained. I found that the results agree very satisfactorily with the prediction of the theory within experimental error. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis concerns itself with the applicability of quantum field methods, in the fixed field approximation, to problems involving a weak gravitational field. After introducing general scattering relations, various classic problems are reviewed to illustrate various approaches to solving scattering problems. Newtonian and quantum mechanical field methods are illustrated using Coulomb scattering. Classical relativity is used to solve the bending of light rays by the sun. Finally, quantum field methods are used to solve the scattering of polarized photons by the sun. The additional problems of scattering of light by a mass distribution and by a rotating mass are calculable using this method. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In order to use inelastic neutron scattering to isomeric levels as a tool in evaluating nuclear strength functions, we derive the appropriate evaporation formulae; both with and without corrections for the statistical fluctuations of the compound nucleus reduced partial widths. The isomeric activity induced by inelastic neutron scattering is calculated for: In¹¹⁵, Rh¹º³, Y⁸⁹ and Nb⁹³; and is used to illustrate the effect of the fluctuation corrections and the level spin and parity assignments, on the calculated cross sections. Comparison with experimental data is used to infer probable assignments of level spins and parities for In¹¹⁵ and Rh¹º³. We also show that for any nucleus lying near an even or odd partial wave strength function resonance, the inelastic neutron scattering cross section to isomeric levels will be directly proportional to l ≥ 2 strength functions. In the examples cited above, it is the d-wave strength function; and the isomeric cross section shows the corresponding dependence on the optical model potential, being directly proportional to the strength of the imaginary part and insensitive to the real part of the potential. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In preparation for laser light scattering experiments on plasmas in magnetic fields a pulsed ruby laser has been developed in conjunction with a multichannel spectral analyser for detection of the scattered light. The laser, consisting of separate oscillator and amplifier rods has a spectral line width of .08 Å at powers up to 100 Megawatts. The use of a Pockels Cell as the Q-switch permits accurate synchronization with the spectral analyser and all external electronics. For the multichannel detection system five fiber optics slit bundles transmit light from the output of a monochromater to five photomultipiier tubes, which are gated on for 100 nsec during the laser pulse. The pulses are displayed sequentially to give an intensity vs. wavelength profile on an oscilloscope screen. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An Optical Model study has "been made for the elastic scattering of 4.2 MeV. neutrons from three heavy nuclei, Lead, Bismuth and Uranium. The Optical Model used included a real, imaginary, and spin-orbit potential well. Its parameters were determined from a least square fitting to the experimental scattering data available in the literature for angles from 15 to 180 degrees. The model is then used to estimate the nuclear scattering to be expected at small scattering angles. It is shown that Schwinger scattering and incident neutron polarization significantly alter the shape of the elastic cross section at angles less than 10 degrees. At 5 degrees this change is about 3%. Additional effects due to Electric Polarizability scattering are shown to be very small and not sufficient for a determination of the polarizability of the neutron from the elastic scattering data at this energy. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Absolute differential cross-sections have been measured for elastic π± scattering on ¹²C, ⁴⁰Ca, and ⁴⁸Ca using the QQD Spectrometer. The ¹²C data are in good agreement with (Sob 84a), indicating that the overall normalization of the data is good. The π⁺ ⁴⁰Ca data does not agree with the previously published data of (Pre 81) but fits the potential calculation using the SET E parameters (Car 82) better. Data for ⁴⁸Ca and π⁻⁴⁰Ca have not been previously published. An optical potential model was used to describe the data. The potential parameters were fixed by fitting to the ⁴⁰Ca absolute cross-sections. The π⁻ differential cross-section ratios of the measured pair, (⁴⁸Ca, ⁴⁰Ca), were compared to calculations for which the ⁴⁸Ca neutron distribution had been fitted, either by varying the Fermi parameters, or by adding a truncated series of orthogonal polynomials to a starting Fermi form. Two forms of orthogonal polynomials were used; spherical Bessel functions as used in (Gyl 84, Bar 85)), and Laguerre polynomials as used in (Bar 85). The rms radii differences obtained from the Fermi form fitting were found not to be independent of the optical potential used and to be sensitive to the inclusion of the ratio data in the diffractive region. Difficulties were encountered in obtaining reliable results from the orthogonal polynomial fits. The rms radii difference produced by the polynomial fits were not in agreement with results from the Fermi function fit. The neutron density distribution difference obtained from the polynomial fit is similar in form to the results of (Ray 81), but the distribution peak is shifted toward the nuclear center. The rms radii differences found from the Fermi function and Fourier-Laguerre analysis are; Fermi Fourier-Laguerre Δnn',.222±.048 .110 ± .022 (fm) / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The growth and saturation characteristics of stimulated Brillouin scattering (SBS) in the interaction of an intense (Ｉ≤ 10¹³ W/cm²) CO₂ laser beam with an underdense plasma are investigated experimentally. The plasma is produced by focussing a short (2 ns FWHM), CO₂ laser pulse onto a stabilized nitrogen gas jet which flows from a Laval nozzle into low pressure helium. The resulting SBS interaction is studied through observations of the intensity and spectral behavior of the backscattered light as well as through temporally resolved ruby laser Thomson scattering measurements of the spatial and spectral behavior of the SBS generated ion acoustic waves. SBS occurs primarily in the long scale length, low density plasma located in the background gas in front of the jet. Initially, the instability grows absolutely at a rate within a factor of two of the predicted temporal growth rate. The SBS reflectivity is observed to saturate at less than 10%. This low reflectivity is a result of two processes. First, the SBS interaction region and the associated ion acoustic waves are broken up into several smaller regions, hence limiting the coherence length of the waves, and second, the ion acoustic fluctuation amplitude saturates at less than 20%. The latter saturation is attributed to trapping of ions within the potential troughs of the ion acoustic waves. The observed occurrence of the first harmonic in the ion acoustic wave spectrum as well as temporal modulations in the wave amplitude and sidebands in the spectrum of the backscattered light can be explained as consequences of the ion trapping. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In this thesis a phenomenology is given with the view to determining the electromagnetic contributions to the low energy πN S-wave phase shifts. The approach we take is to partition the Coulomb potential into a short and a long ranged part at some arbitrary cutoff radius. Subsequently we deduce expressions which allow us to estimate, in two distinct stages, first the short and then the long range electromagnetic modifications to the purely hadronic physical observable quantities. The analysis formally begins with a discussion of the single channel π+p—> π+p elastic scattering process. We then turn our attention to the two channel process π⁻p—> π⁻p, π°n. Although a more complete discussion of π⁻p low energy scattering should necessarily entail the inclusion of the third channel inelastic process π⁻p—> ƴn, we have chosen to ignore this in order that we may elucidate some of the ambiguities that have existed with the two channel analysis. Explicit calculations are done, for the energy range 11.6 Mev ≤ T[sub= π][sup= LAB] ≤ 44.0 Mev. For input we use energy dependent expressions for the hadronic phase shifts. Although our estimates to the Coulomb modifications to these quantities do display the same general features with those found in the literature, the numbers we get for the π⁻p phase shifts are considerably smaller. This we attribute to our omission of the ƴn channel. The encouraging feature we do find however is that the procedure developed for treating both the one and the two channel problems are nearly identical. The only difference is that the latter necessitates the use of the unitarity constraint on the scattering matrix. This we hope will serve as a useful guide for a future discussion of the three channel problem. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In this thesis, a theory of neutrino masses and oscillations is built up in the general case. The work is then restricted to the three-species Dirac case, for which the required parameters, a mass scale and a mixing matrix, are provided by phenomenological solutions and by a new Hierarchial Mass Scheme coupled with both Cabibbo and Hierarchial mixings. The oscillations formalism and hypotheses are then applied to neutrino-electron scattering experiments to be performed at Brookhaven, with neutrino energies ranging from 20 to 270 MeV. The ʋ-e scattering cross-sections, the relevant phenomenological quantities, and the resulting predictions are successively calculated and examined. / Science, Faculty of / Physics and Astronomy, Department of / Graduate