Investigations on states of 20Mg and spallation reaction effects for constraining nuclear physics inputs for X-ray bursts

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dc.contributor.advisor Kanungo, Rituparna
dc.creator Randhawa, Jaspreet
dc.date.accessioned 2017-09-18T14:09:05Z
dc.date.available 2017-09-18T14:09:05Z
dc.date.issued 2017
dc.identifier.other QB464 R36 2017
dc.identifier.uri http://library2.smu.ca/handle/01/27086
dc.description viii, 131 leaves : illustrations (chiefly colored) ; 29 cm
dc.description Includes abstract.
dc.description Includes bibliographical references (leaves 125-131).
dc.description.abstract We present the first observation of a resonance state in the proton drip-line nucleus [superscript 20]Mg. The resonance state was populated via inelastic scattering of [superscript 20]Mg with a solid deuteron target using the IRIS facility stationed at TRIUMF, Canada. Together with the ground state and first excited state, a new resonance state is observed at excitation energy of 3.68 [plus or minus] 0.04 MeV. Based on a comparison of the measured angular distributions to distorted wave Born approximation calculations, the first excited state is consistent with L=2 excitation confirming its spin to be 2+. Similar comparison for new resonance suggests a spin possibility of either (4+) or (2+). The new resonance state lies in the Gamow window and hence puts constraint on the [superscript 18]Ne(2p, gamma)[superscript 20]Mg reaction rate, a possible breakout reaction from hot CNO cycles in X-ray bursts. The new resonance state is higher in energy than expectations based on mirror symmetry to [superscript 20]O. The inferred reaction rate of [superscript 19]Na(p, gamma)[superscript 20]Mg is lower than the previous predictions. The net rate of the [superscript 18]Ne(2p, gamma)[superscript 20]Mg is found to be competitive to beta decay of [superscript 18]Ne only at high densities for it to be a viable breakout path. A comparison to theoretical predictions show that the calculations based on chiral interactions and NN+3N forces fails to explain the observed resonance state. The new data will therefore serve as guidance to benchmark the nuclear structure models and interactions at the drip-line. In a related study of CNO cycles in X-ray bursts, the spallation of the accreted material in the atmosphere of a neutron star has been modelled considering a full cascading destruction process. The results show that the replenishment of CNO elements in a cascading process is minuscule and the CNO abundances are reduced to negligible values. The impact of reduced CNO metallicity on X-ray burst ignition conditions are discussed. en_CA
dc.language.iso en en_CA
dc.publisher Halifax, N.S. : Saint Mary's University
dc.subject.lcc QB464
dc.subject.lcsh Nuclear astrophysics
dc.subject.lcsh Magnesium -- Isotopes
dc.subject.lcsh Spallation (Nuclear physics)
dc.subject.lcsh X-ray bursts
dc.title Investigations on states of 20Mg and spallation reaction effects for constraining nuclear physics inputs for X-ray bursts en_CA
dc.type Text en_CA
thesis.degree.name Doctor of Philosophy in Astronomy
thesis.degree.level Doctoral
thesis.degree.discipline Astronomy and Physics
thesis.degree.grantor Saint Mary's University (Halifax, N.S.)


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