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Wang, Y.-Z., Li, Y., Qi, C. & Gu, J.-Z. (2019). Pairing Effects on Bubble Nuclei. Chinese Physics Letters, 36(3), Article ID 032101.
Open this publication in new window or tab >>Pairing Effects on Bubble Nuclei
2019 (English)In: Chinese Physics Letters, ISSN 0256-307X, E-ISSN 1741-3540, Vol. 36, no 3, article id 032101Article in journal (Refereed) Published
Abstract [en]

In the framework of the Skyrme-Hartree-Fock-Bogoliubov approach with the SkT interaction, the pairing effects on the proton bubble structures of Ar-46 and( 206)Hg are discussed. In calculations, three kinds of pairing forces (volume, surface and mixed pairing interactions) are used. For Ar-46, it is shown that the bubble structure with the volume pairing is almost the same as that with the mixed pairing. The bubble with the surface pairing is less pronounced than those with the volume and mixed pairings. Analyzing the density distributions and occupation probabilities of the proton s states and the quasi-degeneracy between the proton 2s(1/2) and 1d(3/2) orbitals, we explain the difference between the bubble structure with the surface pairing and those with the volume and mixed pairings. For Hg-206, it is seen that the proton density distribution with the surface pairing is different from those with the volume and mixed pairings in the whole region of the radial distance. In addition, it is found that the bubbles with the three pairing forces are different from each other and the least pronounced bubble is obtained with the surface pairing. Thus the selection of the pairing force is important for the study of the nuclear bubble structure.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-247820 (URN)10.1088/0256-307X/36/3/032101 (DOI)000460822000005 ()
Note

QC 20190327

Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2019-03-27Bibliographically approved
Qi, C., Liotta, R. & Wyss, R. A. (2019). Recent developments in radioactive charged-particle emissions and related phenomena. Progress in Particle and Nuclear Physics, 105, 214-251
Open this publication in new window or tab >>Recent developments in radioactive charged-particle emissions and related phenomena
2019 (English)In: Progress in Particle and Nuclear Physics, ISSN 0146-6410, E-ISSN 1873-2224, Vol. 105, p. 214-251Article, review/survey (Refereed) Published
Abstract [en]

The advent and intensive use of new detector technologies as well as radioactive ion beam facilities have opened up possibilities to investigate alpha, proton and cluster decays of highly unstable nuclei. This article provides a review of the current status of our understanding of clustering and the corresponding radioactive particle decay process in atomic nuclei. We put alpha decay in the context of charged-particle emissions which also include one- and two-proton emissions as well as heavy cluster decay. The experimental as well as the theoretical advances achieved recently in these fields are presented. Emphasis is given to the recent discoveries of charged-particle decays from proton-rich nuclei around the proton drip line. Those decay measurements have shown to provide an important probe for studying the structure of the nuclei involved. Developments on the theoretical side in nuclear many-body theories and supercomputing facilities have also made substantial progress, enabling one to study the nuclear clusterization and decays within a microscopic and consistent framework. We report on properties induced by the nuclear interaction acting in the nuclear medium, like the pairing interaction, which have been uncovered by studying the microscopic structure of clusters. The competition between cluster formations as compared to the corresponding alpha-particle formation are included. In the review we also describe the search for super-heavy nuclei connected by chains of alpha and other radioactive particle decays.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Alpha decay, Charged-particle emission, Formation probability, Nuclear structure, Pairing
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-246494 (URN)10.1016/j.ppnp.2018.11.003 (DOI)000461538400006 ()2-s2.0-85058194997 (Scopus ID)
Note

QC 20190320

Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2019-04-05Bibliographically approved
Ertoprak, A., Cederwall, B., Qi, C., Doncel, M., Jakobsson, U., Nyako, B. M., . . . Xiao, Z. G. (2018). M1 and E2 transition rates from core-excited states in semi-magic Ru-94. European Physical Journal A, 54(9), Article ID 145.
Open this publication in new window or tab >>M1 and E2 transition rates from core-excited states in semi-magic Ru-94
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2018 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 54, no 9, article id 145Article in journal (Refereed) Published
Abstract [en]

Lifetimes of high-spin states have been measured in the semi-magic (N = 50) nucleus Ru-94. Excited states in Ru-94 were populated in the Ni-58(Ca-40, 4p)Ru-94* fusion-evaporation reaction at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator complex. DSAM lifetime analysis was performed on the Doppler broadened line shapes in energy spectra obtained from gamma-rays emitted while the residual nuclei were slowing down in a thick 6 mg/cm(2) metallic Ni-58 target. In total eight excited-state lifetimes in the angular momentum range I = (13-20)h have been measured, five of which were determined for the first time. The corresponding B(M1) and B(E2) reduced transition strengths are discussed within the framework of large-scale shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-234570 (URN)10.1140/epja/i2018-12581-7 (DOI)000443091000003 ()2-s2.0-85052645166 (Scopus ID)
Funder
Swedish Research Council, 621-2014-5558Swedish Research Council, 621-2012-3805Swedish Research Council, 621-2013-4323Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
Note

QC 20180917

Available from: 2018-09-19 Created: 2018-09-19 Last updated: 2018-09-19Bibliographically approved
Qian, Y. & Qi, C. (2018). Partial seniority conservation and solvability of single- j systems. Physical Review C: Covering Nuclear Physics, 98(6), Article ID 061303.
Open this publication in new window or tab >>Partial seniority conservation and solvability of single- j systems
2018 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 98, no 6, article id 061303Article in journal (Refereed) Published
Abstract [en]

The seniority symmetry is known to be partially conserved in two special cases in the (9/2)(4) system, which can lead to striking features in the corresponding structure and electromagnetic transition properties. However, it is still quite difficult to derive those kind of solvable states, in general, especially towards higher- j orbits. We have developed a novel and effective way to confront this challenge by starting from the m scheme and making use of the angular momentum projection method. It also allows us to explore another special family of seniority conserving states in the midshell besides the specific case of the (9/2)(4) configuration. Moreover, we have studied systemically all states in single- j systems up to j = 15/2 and derived the analytic expressions for the eigenvalues of all solvable states with a focus on those in j = 9/2 and j = 11/2. Such studies can also be useful for the experimental search of relevant states and for the understanding of their electromagnetic transition properties.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2018
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-241202 (URN)10.1103/PhysRevC.98.061303 (DOI)000454166100001 ()2-s2.0-85059388722 (Scopus ID)
Note

QC 20190118

Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2019-01-18Bibliographically approved
Qi, C. (2017). Differential evolution algorithm for global optimizations in nuclear physics. Journal of Physics G: Nuclear and Particle Physics, 44(4), Article ID 045107.
Open this publication in new window or tab >>Differential evolution algorithm for global optimizations in nuclear physics
2017 (English)In: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 44, no 4, article id 045107Article in journal (Refereed) Published
Abstract [en]

We explore the applicability of the differential evolution algorithm in finding the global minima of three typical nuclear structure physics problems: the global deformation minimum in the nuclear potential energy surface, the optimization of mass model parameters and the lowest eigenvalue of a nuclear Hamiltonian. The algorithm works very effectively and efficiently in identifying the minima in all problems we have tested. We also show that the algorithm can be parallelized in a straightforward way.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Keywords
global minimum, optimization, potential energy surface, eigenvalue
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-206275 (URN)10.1088/1361-6471/aa5f87 (DOI)000395978700002 ()2-s2.0-85015730734 (Scopus ID)
Note

QC 20170512

Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2017-05-12Bibliographically approved
Doncel, M., Cederwall, B., Qi, C., Li, H. J., Jakobsson, U., Auranen, K., . . . Uusitalo, J. (2017). Lifetime measurements of excited states in W-162 and W-164 and the evolution of collectivity in rare-earth nuclei. Physical Review C: Covering Nuclear Physics, 95(4), Article ID 044321.
Open this publication in new window or tab >>Lifetime measurements of excited states in W-162 and W-164 and the evolution of collectivity in rare-earth nuclei
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2017 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 95, no 4, article id 044321Article in journal (Refereed) Published
Abstract [en]

Lifetimes of the first excited 2(+) states in the extremely neutron- deficient W-162 and W-164 nuclei have been measured using the recoil distance Doppler shift technique. Experimental B(E2) data for the isotopic chains of hafnium, tungsten, and osmium, from the midshell region near the beta-stability line towards the N = 82 closed shell and the most neutron-deficient nuclides, are compared with predictions of nuclear deformations and 2(1)(+) -> 0(g.s)(.+) reduced transition strengths from different classes of state-of-the-art theoretical model calculations. The results reveal striking differences and deficiencies in the predictive power of current nuclear structure models.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-207673 (URN)10.1103/PhysRevC.95.044321 (DOI)000400140500006 ()2-s2.0-85018532567 (Scopus ID)
Funder
Swedish Research Council, 621-2014-5558EU, FP7, Seventh Framework Programme, 262010 ENSAR
Note

QC 20170601

Available from: 2017-06-01 Created: 2017-06-01 Last updated: 2017-11-29Bibliographically approved
Qi, C. (2017). Partial conservation of seniority and its unexpected influence on E2 transitions in g(9/2) nuclei. Physics Letters B, 773, 616-619
Open this publication in new window or tab >>Partial conservation of seniority and its unexpected influence on E2 transitions in g(9/2) nuclei
2017 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 773, p. 616-619Article in journal (Refereed) Published
Abstract [en]

There exist two uniquely defined v = 4 states in systems within a j = 9/2 subshell, which automatically conserve seniority and do not mix with other states. Here I show that the partial conservation of seniority plays an essential role in our understanding of the electric quadrupole transitions of the semimagic nuclei involving j = 9/2 subshells, including the long-lived 8(+) isomer in (94) Ru. The effects of configuration mixing from neighboring subshells on the structure of those unique states are analyzed. It is shown that a sharp transition from pure seniority coupling to a significant mixture between the v = 2 and v = 4 states may be induced by the cross-orbital non-diagonal interaction matrix elements. Such strong mixture is essential to explain the observed E2 transition properties of N = 50 isotones Pd-96 and Ru-94.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-217441 (URN)10.1016/j.physletb.2017.09.025 (DOI)000413294200091 ()2-s2.0-85031721049 (Scopus ID)
Note

QC 20171117

Available from: 2017-11-17 Created: 2017-11-17 Last updated: 2017-11-17Bibliographically approved
Wang, F., Sun, B. H., Liu, Z., Qi, C., Zhu, L. H., Scholey, C., . . . Williams, S. (2017). Reinvestigation of the excited states in the proton emitter Lu-151: Particle-hole excitations across the N = Z=64 subshell. Physical Review C: Covering Nuclear Physics, 96(6), Article ID 064307.
Open this publication in new window or tab >>Reinvestigation of the excited states in the proton emitter Lu-151: Particle-hole excitations across the N = Z=64 subshell
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2017 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 96, no 6, article id 064307Article in journal (Refereed) Published
Abstract [en]

The excited states of the proton emitter Lu-151 were reinvestigated in a recoil-decay tagging experiment at the Accelerator Laboratory of the University of Jyvaskyla (JYFL). The level scheme built on the ground state of 151Lu was updated with five new y-ray transitions. Large-scale shell model calculations were carried out in the model space consisting of the neutron and proton orbitals 0g(7/2), Id(5/2), Id(3/2), 2s(1/2), and Oh(1/2) with the optimized monopole interaction in order to interpret the experimental level scheme of Lu-151. It is found that the excitation energies of states above the 27/2(-) and 23/2(+) isomeric levels in Lu-151 can be sensitive to excitations from g(7/2) and d(5/2) to single-particle orbitals above N = Z = 64.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-220457 (URN)10.1103/PhysRevC.96.064307 (DOI)000417129500002 ()2-s2.0-85038397786 (Scopus ID)
Funder
Swedish Research Council, 621-2012-3805 621-2013-4323
Note

QC 20180104

Available from: 2018-01-04 Created: 2018-01-04 Last updated: 2018-01-04Bibliographically approved
Qi, C. (2016). Alpha decay as a probe for the structure of neutron-deficient nuclei. Reviews in Physics, 1, 77-89
Open this publication in new window or tab >>Alpha decay as a probe for the structure of neutron-deficient nuclei
2016 (English)In: Reviews in Physics, ISSN 2405-4283, Vol. 1, p. 77-89Article in journal (Refereed) Published
Abstract [en]

The advent of radioactive ion beam facilities and new detector technologies have opened up new possibilities to investigate the radioactive decays of highly unstable nuclei, in particular the proton emission, α decay and heavy cluster decays from neutron-deficient (or proton-rich) nuclei around the proton drip line. It turns out that these decay measurements can serve as a unique probe for studying the structure of the nuclei involved. On the theoretical side, the development in nuclear many-body theories and supercomputing facilities have also made it possible to simulate the nuclear clusterization and decays from a microscopic and consistent perspective. In this article we would like to review the current status of these structure and decay studies in heavy nuclei, regarding both experimental and theoretical opportunities. We then discuss in detail the recent progress in our understanding of the nuclear α formation probabilities in heavy nuclei and their indication on the underlying nuclear structure.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Alpha decay, Neutron-deficient nuclei, Nuclear structure, Pairing
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-195228 (URN)10.1016/j.revip.2016.05.001 (DOI)2-s2.0-84973137721 (Scopus ID)
Note

QC 20161117

Available from: 2016-11-17 Created: 2016-11-02 Last updated: 2016-11-17Bibliographically approved
Wu, Z., Changizi, S. & Qi, C. (2016). Empirical residual neutron-proton interaction in odd-odd nuclei. PHYSICAL REVIEW C, 93(3), Article ID 034334.
Open this publication in new window or tab >>Empirical residual neutron-proton interaction in odd-odd nuclei
2016 (English)In: PHYSICAL REVIEW C, ISSN 2469-9985, Vol. 93, no 3, article id 034334Article in journal (Refereed) Published
Abstract [en]

Two types of average neutron-proton interaction formulas are compared: In the first type, neutron-proton interactions for even-even and odd-A nuclei extracted from experimental binding energies show a smooth behavior as a function of mass number A and are dominated by the contribution from the symmetry energy. Whereas in the second type large systematic staggering is seen between even-A and odd-A nuclei. This deviation is understood in terms of the additional neutron-proton interaction in odd-odd nuclei relative to the neighboring even-even and odd-A systems. We explore three possible ways to extract this additional interaction from the binding energy difference of neighboring nuclei. The extracted interactions are positive in nearly all cases and show weak dependence on the mass number. The empirical interactions are also compared with theoretical values extracted from recent nuclear mass models where large unexpected fluctuations are seen in certain nuclei. The reproduction of the residual neutron-proton interaction and the correction of those irregular fluctuations can be a good criterion for the refinement of those mass models.

Place, publisher, year, edition, pages
American Physical Society, 2016
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-185626 (URN)10.1103/PhysRevC.93.034334 (DOI)000373105400001 ()2-s2.0-84963682697 (Scopus ID)
Funder
Swedish Research Council, 621-2012-3805, 621-2013-4323
Note

QC 20160429

Available from: 2016-04-29 Created: 2016-04-25 Last updated: 2017-11-14Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1406-5695

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