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Multistep Shell Model in the Complex Energy Plane
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis the properties of unbound nuclei like 12,13Li are studiedby extending the multistep shell model to the complex energy plane. Thenuclei 12Li and 13Li are described starting from the one-particle states in 10Liand two-particle states in 11Li. The ground state of 12Li is found to be anantibound state. No bound or antibound state is found in 13Li. It is alsoshown that the odd proton plays a minor role in these nuclei.This framework is also applied to study the recently proposed spin-alignedproton-neutron pair coupling scheme. For this the MSM is extended to theproton-neutron space as well as the isospin space. In the model, a nonorthogonalbasis is introduced, which allows us to identify simultaneously theroles played by all configurations. The four-particle, six-particle and eightparticlenuclei in the heaviest N = Z region are evaluated using the MSMbasis within the space spanned by the single 0g9/2 hole shell.A novel Monte Carlo representation in the complex energy plane is alsodeveloped for studying nuclear excitations in the continuum. The calculationson realistic potentials show a stable performance and high accuracy in the oneparticleand two-particle cases. This will provide a convenient tool to studyopen systems with many nucleons in the continuum.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , ix, 81 p.
Series
Trita-FYS, ISSN 0280-316X ; 2012:81
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:kth:diva-103867ISBN: 978-91-7501-524-8 (print)OAI: oai:DiVA.org:kth-103867DiVA: diva2:562095
Public defence
2012-11-15, FA32, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20121025

Available from: 2012-10-25 Created: 2012-10-23 Last updated: 2012-11-26Bibliographically approved
List of papers
1. Analysis of the unbound spectrum of 12Li.
Open this publication in new window or tab >>Analysis of the unbound spectrum of 12Li.
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2011 (English)In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 850, 53-68 p.Article in journal (Refereed) Published
Abstract [en]

The unbound nucleus 12Li is evaluated by studying three-neutron one-proton excitations within the multistepshell model in the complex energy plane. It is found that the ground state of this system consists of anantibound 2− state. A number of narrow states at low energy are found which ensue from the coupling ofresonances in 11Li to continuum states close to threshold.

Keyword
Shell model, Berggren representation, 12Li
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-30286 (URN)10.1016/j.nuclphysa.2010.12.003 (DOI)000287270000004 ()2-s2.0-78651363890 (Scopus ID)
Funder
Swedish Research Council, 623-2009-7340 2010-4723
Note
QC 20110222Available from: 2011-02-21 Created: 2011-02-21 Last updated: 2017-12-11Bibliographically approved
2. Multistep shell model description of spin-aligned neutron-proton pair coupling
Open this publication in new window or tab >>Multistep shell model description of spin-aligned neutron-proton pair coupling
Show others...
2012 (English)In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 877, 51-58 p.Article in journal (Refereed) Published
Abstract [en]

The recently proposed spin-aligned neutron-proton pair coupling scheme is studied within a non-orthogonal basis in term of the multistep shell model. This allows us to identify simultaneously the roles played by other configurations such as the normal pairing term. The model is applied to four-, six- and eight-hole N = Z nuclei below the core Sn-100.

Keyword
Spin-aligned neutron-proton pair, Multistep shell model, 0(g9/2) shell
National Category
Subatomic Physics
Research subject
SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-74396 (URN)10.1016/j.nuclphysa.2011.12.005 (DOI)000301612400004 ()2-s2.0-84856775848 (Scopus ID)
Funder
Swedish Research Council, 623-2009-7340  621-2010-4723Swedish e‐Science Research Center
Note
QC 20120411Available from: 2012-02-03 Created: 2012-02-03 Last updated: 2017-12-08Bibliographically approved
3. Novel Monte Carlo representation for shell model in the complex energy plane
Open this publication in new window or tab >>Novel Monte Carlo representation for shell model in the complex energy plane
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A Monte Carlo method is presented to evaluate quantum states with many particles moving inthe continuum. The scattering state is generated at each time by a Monte Carlo random samplingalgorithm. The same calculation are repeated until the average energies of all calculations converge.For systems with one and two particles, our calculations show that the exact solution can beapproached with around only one hundred iterations.

National Category
Physical Sciences Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-103757 (URN)
Funder
Swedish Research Council, 621-2010-4723
Note

QS 2012

Available from: 2012-10-23 Created: 2012-10-19 Last updated: 2012-10-25Bibliographically approved
4. Shell evolution and its indication on the isospin dependence of the spin-orbit splitting
Open this publication in new window or tab >>Shell evolution and its indication on the isospin dependence of the spin-orbit splitting
2013 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 724, no 4-5, 247-252 p.Article in journal (Other academic) Published
Abstract [en]

The available experimental data on shell evolution indicate that the strength of the spin-orbit single-particle potential may be enhanced in neutron-rich nuclei. We observe that such a simple scheme destroys the harmonic oscillator magic numbers N = 8 and 20 and generates new magic numbers like N = 6, 14, 16, 32 and 34. The traditional magic numbers like N = 28 and 50 and N = 14 seen in O-22 are eroded in neutron-rich nuclei due to the sensitivity of larger-l orbitals to the depth of the central potential but they are more robust than the harmonic oscillator magic numbers. The N = 82 shell closure persists in neutron-rich nuclei while the previously proposed shell closures like N = 40 and 70 do not emerge. Both mechanisms contribute to enhancing the N = 56 and 90 gaps by splitting the 1d(5/2) and 0g(7/2) and the 0h(9/2) and 1f(7/2) orbitals.

Keyword
Shell evolution; Woods-Saxon potential; Spin-orbit coupling; Isospin dependence
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-103900 (URN)10.1016/j.physletb.2013.06.018 (DOI)000322358500007 ()2-s2.0-84880315652 (Scopus ID)
Funder
Swedish Research Council, 621-2010-4723 621-2012-3805
Note

QC 20160531

Available from: 2012-10-24 Created: 2012-10-24 Last updated: 2017-12-07Bibliographically approved
5. Alternate proof of the Rowe-Rosensteel proposition and seniority conservation
Open this publication in new window or tab >>Alternate proof of the Rowe-Rosensteel proposition and seniority conservation
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2010 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 82, no 1, 014304- p.Article in journal (Refereed) Published
Abstract [en]

For a system with three identical nucleons in a single-j shell, the states can be written as the angular-momentum coupling of a nucleon pair and the odd nucleon. The overlaps between these nonorthonormal states form a matrix that coincides with the one derived by Rowe and Rosensteel [Phys. Rev. Lett. 87, 172501 ( 2001)]. The propositions they state are related to the eigenvalue problems of the matrix and dimensions of the associated subspaces. In this work, the propositions are proven from the symmetric properties of the 6j symbols. Algebraic expressions for the dimension of the states, eigenenergies, as well as conditions for conservation of seniority can be derived from the matrix.

Keyword
SHELL
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-29478 (URN)10.1103/PhysRevC.82.014304 (DOI)000279940200002 ()2-s2.0-77954649717 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20110207Available from: 2011-02-07 Created: 2011-02-02 Last updated: 2017-12-11Bibliographically approved
6. Multistep shell model in the complex energy plane
Open this publication in new window or tab >>Multistep shell model in the complex energy plane
2012 (English)In: Advanced Many-Body And Statistical Methods In Mesoscopic Systems, Institute of Physics Publishing (IOPP), 2012, 012029- p.Conference paper, Published paper (Refereed)
Abstract [en]

We have adopted the multistep shell model in the complex energy plane to study nuclear excitations occurring in the continuum part of the spectrum. In this method one proceeds by solving the shell model equations in a successive manner. That is, in each step one constructs the building blocks to be used in future steps. We applied this formalism to analyze the unbound nuclei Li-12,Li-13 starting from the one - particle states in Li-10 and two - particle states in Li-11. In the former case the excitations correspond to the motion of three particles partitioned as the product of a one - particle and two - particle systems. The ground state of Li-12 is thus calculated to be an antibound (virtual) state. In the four - particle system Li-13 the states can be constructed as the coupling of two correlated pairs. We found that there is no bound or antibound state in Li-13.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2012
Series
Journal of Physics: Conference Series, ISSN 1742-6588 ; 338
Keyword
States, Representation
National Category
Subatomic Physics
Research subject
SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-74463 (URN)10.1088/1742-6596/338/1/012029 (DOI)000304599800029 ()2-s2.0-84859534182 (Scopus ID)
Conference
Advanced Many-Body and Statistical Methods in Mesoscopic Systems; Constanta; 27 June 2011 through 2 July 2011
Funder
Swedish e‐Science Research Center
Note

QC 20120626

Available from: 2012-02-03 Created: 2012-02-03 Last updated: 2012-10-25Bibliographically approved
7. Analytic proof of partial conservation of seniority in j=9/2 shells
Open this publication in new window or tab >>Analytic proof of partial conservation of seniority in j=9/2 shells
2012 (English)In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 884, 21-35 p.Article in journal (Refereed) Published
Abstract [en]

A partial conservation of the seniority quantum number in j = 9/2 shells has been found recently in a numerical application. In this paper an analytic proof for this problem is derived as an extension of the work [L. Zamick, P. Van Isacker, Phys. Rev. C 78 (2008) 044327]. We analyze the properties of the non-diagonal interaction matrix elements with the help of the one-particle and two-particle coefficients of fractional parentage (cfp's). It is found that all non-diagonal (and the relevant diagonal) matrix elements can be re-expressed in simple ways and are proportional to certain one-particle cfp's. This remarkable occurrence of partial dynamic symmetry is the consequence of the peculiar property of the j = 9/2 shell, where all it = 3 and 5 states are uniquely defined.

Keyword
Seniority, Partial symmetry, Coefficients of fractional parentage
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-98918 (URN)10.1016/j.nuclphysa.2012.04.007 (DOI)000305305200002 ()2-s2.0-84860809011 (Scopus ID)
Note
QC 20120713Available from: 2012-07-13 Created: 2012-07-05 Last updated: 2017-12-07Bibliographically approved
8. Monopole-optimized effective interaction for tin isotopes
Open this publication in new window or tab >>Monopole-optimized effective interaction for tin isotopes
2012 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 86, no 4, 044323- p.Article in journal (Refereed) Published
Abstract [en]

We present a systematic configuration-interaction shell-model calculation on the structure of light tin isotopeswith a global optimized effective interaction. The starting point of the calculation is the realistic CD-Bonnnucleon-nucleon potential. The unknown single-particle energies of the 1d3/2, 2s1/2, and 0h11/2 orbitals and theT = 1 monopole interactions are determined by fitting to the binding energies of 157 low-lying yrast states in102−132Sn. We apply the Hamiltonian to analyze the origin of the spin inversion between 101Sn and 103Sn that wasobserved recently and to explore the possible contribution from interaction terms beyond the normal pairing.

Place, publisher, year, edition, pages
American Physical Society, 2012
Keyword
Light Sn Isotopes, Shell-Model, Generalized Seniority, Nuclei, Even, Isomers, States
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-103754 (URN)10.1103/PhysRevC.86.044323 (DOI)000309998900002 ()2-s2.0-84867785440 (Scopus ID)
Funder
Swedish Research Council, 621-2010-4723
Note

QC 20121031

Available from: 2012-10-31 Created: 2012-10-19 Last updated: 2017-12-07Bibliographically approved

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Output format
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