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Competition Effects in Charged Particle Induced Reactions


Zyskind, John Lehrer (1979) Competition Effects in Charged Particle Induced Reactions. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/dtne-cd02.


Absolute cross sections have been measured for 14 reactions: 54Cr(p,γ)55Mn for 0.83 MeV ≤ Ep ≤ 3.61 MeV, 54Cr(p,n)54Mn for 2.23 MeV < Ep < 3.61 MeV, 51V(p,γ)52Cr for 0.93 Mev, < Ep < 4.47 MeV, 51V(p,n)51Cr for 1.58 MeV < Ep < 4.47 MeV, 68Zn(p,γ)69Ga for 1.67 MeV ≤ Ep ≤ 4.97 MeV, 68Zn(p,n)68Ga for 3.77 MeV ≤ Ep ≤ 5.03 MeV, 68Zn(p,α)65Cu for 3.36 MeV ≤ Ep ≤ 5.48 MeV, 48Ca(p,γ)44Sc for 0.58 MeV ≤ Ep ≤ 2.67 MeV, 48Ca(p,n)48Sc for 0.96 ≤ Ep ≤ 2.67 MeV, 37Cl(a,γ)41K for 2.90 Mev ≤ Eα ≤ 5.23 MeV, 62Ni(α,γ)66Zn for 5.07 MeV ≤ Eα ≤ 8.64 MeV, 62Ni(α,n)65Zn for 6.95 MeV ≤ Eα ≤ 8.76 MeV, 64Ni(α,γ)68Zn for 4.50 MeV ≤ Eα ≤ 7.45 MeV, and 64Ni(α,n)67Zn for 5.29 ≤ Eα ≤ 7.44 MeV. Substantial drops in cross sections, by factors from three to five, were observed above the neutron thresholds for all of the radiative capture reactions except 48Ca(p,γ)49Sc. These “competition cups” are caused by competition from the neutron channel. In the 48Ca(p,γ)49Sc and 68Zn(p,α)65Cu reactions, significant though smaller neutron competition effects were observed. The measured cross sections have been compared with cross sections calculated using global Hauser-Feshbach models. It was thus established that: (i) isospin mixing should be assumed to be complete in these nuclear reaction models, (ii) width fluctuation corrections should be included in the treatment of the competition effects, and (iii) black nucleus strength functions for the neutron channels lead to inadequate neutron transmission functions, and should be replaced by more realistic strength functions which include the effects of size resonances. Cross sections calculated with current versions of global Hauser-Feshbach models, which incorporate these modifications, agree with those measured for the fourteen reactions studies to within a factor of two in almost all cases, and to within a factor of three in all cases.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Barnes, Charles A. (advisor)
  • Fowler, William A. (co-advisor)
Thesis Committee:
  • Barnes, Charles A.
  • Fowler, William A.
Defense Date:21 May 1979
Funding AgencyGrant Number
Fannie and John Hertz FoundationUNSPECIFIED
Record Number:CaltechTHESIS:10092018-083946154
Persistent URL:
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URLURL TypeDescription adapted for Appendix A. adapted for Appendix B.
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11223
Deposited By: Tony Diaz
Deposited On:09 Oct 2018 22:16
Last Modified:19 Apr 2021 22:27

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