Thesis (Ph. D.)--Cornell University, 1917.

Thesis (Ph. D.)--University of Chicago, 1916. / "A Private edition distributed by the University of Chicago Libraries." "Reprinted from the Physical review, n.s., vol. VIII, no. 4, October, 1916." Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Chicago, 1909. / "Reprinted from the Physical review, vol. XXX, no. 1, January, 1910." Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Chicago, 1916. / "A Private edition distributed by the University of Chicago Libraries." "Reprinted from the Physical review, N.S., Vol. VIII, No. 6, December, 1916." Includes bibliographical references. Also available on the Internet.

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

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

By the technique of adiabatic demagnetization, paramagnetic salts may be cooled to temperatures less than .1°K. By good thermal contact between crystals and paramagnetic salts, the antiferromagnetics MnSiF₆.6H₂0 and CoC1₂.6H₂0 were cooled to temperatures at which the hyperfine interaction energy of an introduced Mn⁵⁴ impurity was comparable to kT. This resulted in a preferential population distribution of the available energy states. The alignment of nuclear spin, induced by the crystalline field present at the active Mn⁵⁴ impurity, was measured by the anisotropic distribution of the ƴ-rays given off by the radioactive Mn⁵⁴. This data led to a determination of the crystalline field acting on the impurity ion in MnSiF₆.6H₂0 and to verification of theoretical calculations representing the anisotropy of ƴ-emission as a function of absolute temperature. Also by means of such data, a determination was made of the axes of alignment in the antiferromagnetic, CoC1₂.6H₂0 . / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis describes the design and construction of an instrument for comparison of x-ray doses at two different points in an x-ray field. Essentially, it consists of two ionization chambers each fed into a very stable, linear, d.c. amplifier. The outputs of the d.c. amplifiers are coupled in such a way that a fraction of the output of one amplifier is balanced against the total output of the other in a ratio circuit. The scale of the ratio circuit may be set to read directly the dose at any point as a percentage of the dose at an arbitrarily chosen reference point. This percentage is independent of fluctuations of the x-ray intensity with time. The instrument is battery-operated, light in weight and therefore easily portable. The principal use of the instrument is for the comparison of x-ray doses at different points in a tissue-equivalent medium — information required for dose estimates in radiotherapy. The accuracy of the instrument is better than one half percent of the maximum dose in the x-ray field. The instrument can be modified for automatic plotting of "isodose curves". / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis is devoted to some aspects of the theory of the weak continuous gamma radiation (often called 'Internal Bremsstrahlung') which accompanies beta processes, i.e. negative and positive electron emission and orbital electron capture. Whenever a beta process is accompanied by this gamma radiation, it will be called a "radiative" beta process, otherwise "radiationless". The results presented in this thesis go beyond those obtained by other authors in two respects. In the first place, the radiative beta emission probability is calculated for an allowed transition taking into account an arbitrary mixture of all the five beta interactions. Previously, only the theory for the case of pure interactions has been carried out. In the calculations, as in previous ones, Coulomb effects have been neglected. In the second place, the radiative K capture probability is calculated for an all owed transition taking into account again an arbitrary mixture of the five beta interactions, and, in addition, Coulomb effects. Previously, only the case of pure interactions with the neglection of Coulomb effects has been considered. In order to take Coulomb effects into account, a "semi-relativistic" approximation for the solutions to the Dirac equation with a Coulomb potential has been developed. It turns out that taking Coulomb effects into account reduces the probability of radiative K capture by an order of magnitude. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The gamma rays resulting from the bombardment of B¹⁰ with protons of energies from 0.5 to 2.0 Mev. have been observed with a sodium iodide scintillation counter. Capture radiation, of energy E[subscript γ] = 8.81 ± 0.05 + 10/11 E[subscript p] Mev., showed a broad resonance at E[subscript p] = 1135 ± 15 kev. At this energy, the radiation had an angular distribution of the form 1 + (0.5 ± 0.05)cos²θ and a total cross section (3.5 ± 1.0) × 10[power -30] cm². Several lower energy radiations were also observed and assigned tentatively to cascade transitions in en. The cross section for the 430 kev. radiation from the reaction B¹⁰ (p, αγ)Be⁷ was measured to be 0.21 ± 0.05 bn. at E[subscript p] = 1.52 Mev. This radiation was found to be isotropic. A three crystal scintillation counter pair spectometer has been constructed and used to observe the gamma radiations from the bombardment of B¹⁰ with deuterons of energies from 0.6 to 2.0 Mev. The spectrometer incorporated a selection of those pulses in the side counters representing 0.5 Mev. energy release before they entered a triple coincidence circuit, responding to coincidence between the three counters. The improved energy resolution and background rejection allowed the complex gamma ray spectra from B¹⁰ + d to be resolved and interpreted. / Science, Faculty of / Physics and Astronomy, Department of / Graduate