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A Theoretical Investigation of Bound Roton Pairs in Superfluid Helium-4

Description: The Bogoliubov theory of excitations in superfluid helium is used to study collective modes at zero temperature. A repulsive delta function shell potential is used in the quasiparticle excitation energy spectrum to fit the observed elementary excitation spectrum, except in the plateau region. The linearized equation of motion method is used to obtain the secular equation for a collective mode consisting of a linear combination of one and two free quasiparticles of zero total momentum. It is sho… more
Date: August 1974
Creator: Cheng, Shih-ta
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

K-Shell Ionization Cross Sections of Selected Elements from Fe to As for Proton Bombardment from 0.5 to 2.0 MeV

Description: The problem with which this investigation is concerned is that of making experimental measurements of proton-induced K-shell x-ray production cross sections and to study the dependence of these cross sections upon the energy of the incident proton. The measurements were made by detection of the characteristic x-rays emitted as a consequence of the ionization of the K-shell of the atom. The method for relating this characteristic x-ray emission to the x-ray production cross section is discussed … more
Date: December 1973
Creator: Lear, Richard Dean
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

K-Shell Ionization Cross Sections For Elements Se To Pd: 0.4 To 2.0 MeV

Description: K-Shell ionization cross section for protons over the energy range of 0.4 to 2.0 MeV have been measured on thin targets of the elements Se, Br, Rb, Sr, Y, Mo and Pd. Total x-ray and ionization cross sections for the K-shell are reported. The experimental values of the ionization cross sections are compared to the non-relativistic plane-wave Born approximation, the binary-encounter approximation, the constrained binary-encounter approximation, and the plane-wave Born approximation with correctio… more
Date: December 1974
Creator: Criswell, Tommy L.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Proton-Induced L-shell X-Rays of Pr, Sm, Eu, Gd, and Dy

Description: Characteristic L-shell x rays of the five rare earths Pr, Sm, Eu, Gd, and Dy were studied in this work. The x rays were produced by ionization from 0.3 to 2.0 MeV protons from the 2.0 MV Van de Graaff at North Texas State University. Total L-shell ionization and x-ray production cross sections were measured for Sm and compared to the BEA, CBEA and PWBA theories. Total L-shell ionization cross sections were measured for Pr, Eu, Gd, and Dy and compared to the BEA, CBEA, and PWBA. The CBEA and PW… more
Date: August 1974
Creator: Abrath, Frederick G.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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