K -Shell ionization cross sections of the elements praseodymium, neodymium, samarium, thulium, tantalum, and tungsten for 1-3 MeV protons.
Item
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Title
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K -Shell ionization cross sections of the elements praseodymium, neodymium, samarium, thulium, tantalum, and tungsten for 1-3 MeV protons.
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Identifier
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AAI9000029
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identifier
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9000029
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Creator
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Guardala, Noel Adam.
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Contributor
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Adviser: Evan T. Williams
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Date
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1989
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Nuclear
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Abstract
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We have attempted to measure with an improved degree of accuracy the values of the K-Shell ionization cross section, {dollar}\sigma\sb{lcub}\rm KI{rcub}{dollar}, for selected elements in the region, 59 {dollar}\leq{dollar} Z {dollar}\leq{dollar} 74, using 1.0-3.0 MeV H{dollar}\sp{lcub}+{rcub}{dollar} as the projectiles. This is a region of the Periodic Table where due to the strong permanent deformations, {dollar}\beta\sb0{dollar}, of the nuclear ground state, the values of the nuclear Coulomb excitation cross sections, {dollar}\sigma\sb{lcub}\rm CE{rcub}{dollar}, become comparable in magnitude to the values of {dollar}\sigma\sb{lcub}\rm KI{rcub}{dollar} for the direct atomic collision process.;Not only are the two inelastic channels comparable in overall magnitude, but because the same nuclear states that are easily populated by CE tend to decay primarily by K-Shell internal conversion. This nuclear deexicitation process results in the emission of K x-rays which are identical to the K x-rays produced by direct atomic ionization, DAI. This means that the yields of K x-rays produced in these types of collisions must be corrected for by either calculating the values of {dollar}\sigma\sb{lcub}\rm CE{rcub}{dollar} or by measuring the yields of CE {dollar}\gamma{dollar}-rays. The portion of K x-rays arising from the CE channel can then be subtracted from the total yield of K x-rays.;We have tried the strategy of using where possible isotopes which have smaller values of {dollar}\beta\sb0{dollar}, and therefore smaller values of {dollar}\sigma\sb{lcub}\rm CE{rcub}{dollar}, as a means of practically eliminating the CE contribution to the yield of K x-rays. Where no spherical isotopes exist, we have attempted to both calculate and to measure the yield of CE {dollar}\gamma{dollar}-rays to a high level of accuracy and then use the appropriate internal conversion coefficients, ICC. This was done to arrive at the "true" amount of K x-rays coming from CE.;The other experimental goal of the thesis was the development of a new normalization method using the characteristics L{dollar}\sb{lcub}\gamma1{rcub}{dollar} and L{dollar}\sb{lcub}\gamma2,3{rcub}{dollar} x-rays of the elements studied. This method was compared to the already established normalization methods which uses either Rutherford back-scattering, RBS, or CE {dollar}\gamma{dollar}-rays (when the values of {dollar}\sigma\sb{lcub}\rm CE{rcub}{dollar} are large enough). Significant attention was paid to the determination of the absolute energy efficiency calibration of an intrinsic Ge photon detector. The photon energy range covered in the calibration was 4.0-160 keV. This range of energy includes all the L x-rays of the elements studied up to the higher energies typical of the {dollar}\gamma{dollar}-rays produced by CE of the most deformed nuclides.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
