Study of Proton Emission in Complex Nuclei
(2016) PHYM01 20152Mathematical Physics
Department of Physics
 Abstract
 In a recent experiment, the partial halflife (t_{1/2}) of proton emission from the I^{π} = 19/2^{} state of ^{53}Co was accurately measured. A previous estimate is t_{1/2} ~ 17 s. The purpose of this thesis was to explain this decay and give a theoretical estimate for the dominating hindrance factors.
The angular momentum J in ^{53}Co is coupled to J = 6 for the neutrons, and J = 7/2 for the protons. All of this is transferred to the emitted proton during the decay. In a first approach, the neutron part was ignored and spherical symmetry assumed. Three different methods to describe this decay were tested and compared. These methods were validated... (More)  In a recent experiment, the partial halflife (t_{1/2}) of proton emission from the I^{π} = 19/2^{} state of ^{53}Co was accurately measured. A previous estimate is t_{1/2} ~ 17 s. The purpose of this thesis was to explain this decay and give a theoretical estimate for the dominating hindrance factors.
The angular momentum J in ^{53}Co is coupled to J = 6 for the neutrons, and J = 7/2 for the protons. All of this is transferred to the emitted proton during the decay. In a first approach, the neutron part was ignored and spherical symmetry assumed. Three different methods to describe this decay were tested and compared. These methods were validated by comparing computed reference halflives to Ref. 1 and ^{53}Co halflife to results obtained from the computational code GAMOW (Ref. 2). Assuming this model, all of these methods were accurate, and a method based on probability flow was selected for further calculations. For ^{53}Co, the computed halflife was ~ 17 orders of magnitude too low in the first approach.
The method was improved by including the pairing interaction, giving an increase in t_{1/2} by ~ 1.4. Next, nuclear deformation was included, and both proton and neutron overlaps were computed for different deformations β_{2} of the mother nucleus, assuming axial symmetry. The proton overlap had only a minor effect on the decay time. The increase in angular momentum from ℓ = 3 to ℓ = 9 was estimated to add a factor of ~ 3∙10^{6} to the decay time, and the ℓ = 9 components of the proton wave function another factor of ~ 4∙10^{8}  7∙10^{9}. The remaining factor was conjectured to come from the neutron overlap, but in the model used, this was computed to be zero. This was expected to be resolved by extension to triaxial shapes. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/studentpapers/record/8851250
 author
 Adolfsson, Jonatan ^{LU}
 supervisor

 Gillis Carlsson ^{LU}
 Sven Åberg ^{LU}
 organization
 course
 PHYM01 20152
 year
 2016
 type
 H2  Master's Degree (Two Years)
 subject
 keywords
 Nuclear physics, Nuclear theory, Nuclei far from stability, Proton decay, Cobalt53
 report number
 LundmPh16/01
 language
 English
 id
 8851250
 date added to LUP
 20160511 12:52:35
 date last changed
 20160530 08:57:35
@misc{8851250, abstract = {In a recent experiment, the partial halflife ([i]t[/i][sub]1/2[/sub]) of proton emission from the [i]I[/i][sup]π[/sup] = 19/2[sup][/sup] state of [sup]53[/sup]Co was accurately measured. A previous estimate is [i]t[/i][sub]1/2[/sub] ~ 17 s. The purpose of this thesis was to explain this decay and give a theoretical estimate for the dominating hindrance factors. The angular momentum [i]J[/i] in [sup]53[/sup]Co is coupled to [i]J[/i] = 6 for the neutrons, and [i]J[/i] = 7/2 for the protons. All of this is transferred to the emitted proton during the decay. In a first approach, the neutron part was ignored and spherical symmetry assumed. Three different methods to describe this decay were tested and compared. These methods were validated by comparing computed reference halflives to Ref. 1 and [sup]53[/sup]Co halflife to results obtained from the computational code GAMOW (Ref. 2). Assuming this model, all of these methods were accurate, and a method based on probability flow was selected for further calculations. For [sup]53[/sup]Co, the computed halflife was ~ 17 orders of magnitude too low in the first approach. The method was improved by including the pairing interaction, giving an increase in [i]t[/i][sub]1/2[/sub] by ~ 1.4. Next, nuclear deformation was included, and both proton and neutron overlaps were computed for different deformations [i]β[/i][sub]2[/sub] of the mother nucleus, assuming axial symmetry. The proton overlap had only a minor effect on the decay time. The increase in angular momentum from [i]ℓ[/i] = 3 to [i]ℓ[/i] = 9 was estimated to add a factor of ~ 3∙10[sup]6[/sup] to the decay time, and the [i]ℓ[/i] = 9 components of the proton wave function another factor of ~ 4∙10[sup]8[/sup]  7∙10[sup]9[/sup]. The remaining factor was conjectured to come from the neutron overlap, but in the model used, this was computed to be zero. This was expected to be resolved by extension to triaxial shapes.}, author = {Adolfsson, Jonatan}, keyword = {Nuclear physics,Nuclear theory,Nuclei far from stability,Proton decay,Cobalt53}, language = {eng}, note = {Student Paper}, title = {Study of Proton Emission in Complex Nuclei}, year = {2016}, }