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Cai, B., Chen, G., Xu, J., Yuan, C., Qi, C. & Yao, Y. (2020). alpha decay half-life estimation and uncertainty analysis. Physical Review C: Covering Nuclear Physics, 101(5), Article ID 054304.
Open this publication in new window or tab >>alpha decay half-life estimation and uncertainty analysis
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2020 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 101, no 5, article id 054304Article in journal (Refereed) Published
Abstract [en]

Background: alpha decay is one of the most important decay modes of atomic nuclei. The half-life of alpha decay provides valuable information for nuclear structure study. Many theoretical models and empirical formulas have been suggested to describe the half-life of alpha decay as a function of decay energy (Q(alpha)), atomic number (Z), nucleon number (A), and other related variables. However, the analysis of theoretical uncertainty is rarely done for those alpha decay models. Purpose: We aim to perform a systematic and detailed study on the theoretical uncertainty of existing alpha decay formulas based on statistical methods. Methods: The nonparametric bootstrap method is used to evaluate the uncertainties of two alpha decay formulas, the universal decay law (UDL) and the new Geiger-Nuttall law (NGNL). Such a method can simultaneously obtain the uncertainty of each parameter, the correlation between each pair of parameters, and the total, statistical, and systematic uncertainties of each formula. Both even-even (ee) nuclei and odd-A (oA) nuclei are used in the analysis. The collected data are separated into three parts: ee nuclei, oA nuclei without spin or parity change (oA_nc), and oA nuclei with spin and/or parity change (oA_c). Based on the residues between observed data and corresponding calculations, the statistical and systematic uncertainties are decomposed from the total uncertainty, from which one can clarify the effects from the shell structure, pairing, and angular momentum change on describing alpha decay half-life. Results: If N > 126 and N <= 126 nuclei are considered together, the systematic uncertainty of residues between observed and predicted half-lives are larger than if those groups are considered separately. Without a shell correction term, a much larger systematic uncertainty is found if parameters obtained for N <= 126 nuclei are used to describe the half-lives of N > 126 nuclei. Based on the Bohr-Sommerfeld quantization condition and simple assumptions, a detailed shell correction term is obtained for N > 126 nuclei, for which the value is similar to that in NGNL. A global hindrance on the alpha decay process is found in oA_nc (oA_c) nuclei compared with ee (oA_nc) nuclei. If parameters obtained from ee (oA_nc) nuclei are used, the half-lives of oA_nc (oA_c) nuclei are generally underestimated with large systematic uncertainties, which can be related to the contribution of pairing effect and angular momentum. The parameter of angular momentum term in NGNL is obtained with large uncertainty and very sensitive to the selections of the dataset. The recently observed superallowed decay from Te-104 to Sn-100 is also discussed based on uncertainty analysis. Conclusions: The theoretical uncertainty of existing alpha decay formulas is successfully evaluated by the nonparametric bootstrap method, which simultaneously indicates the important effect in alpha decay, such as the shell effect and the pairing effect. In addition, statistical results show strong correlations between the parameters of the second and third terms in both UDL and NGNL, which demands further investigations.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-273491 (URN)10.1103/PhysRevC.101.054304 (DOI)000530027200001 ()
Note

QC 20200525

Available from: 2020-05-25 Created: 2020-05-25 Last updated: 2020-05-25Bibliographically approved
Ertoprak, A., Cederwall, B., Qi, C., Aktas, Ö., Hadinia, B., Liotta, R., . . . Wyss, R. A. (2020). Evidence for octupole collectivity in Pt-172. European Physical Journal A, 56(2), Article ID 65.
Open this publication in new window or tab >>Evidence for octupole collectivity in Pt-172
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2020 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 56, no 2, article id 65Article in journal (Refereed) Published
Abstract [en]

Excited states in the extremely neutron-deficient nucleus Pt-172 were populated via Ru-96(Kr-78, 2p) and Mo-92(Kr-83, 3n) reactions. The level scheme has been extended up to an excitation energy of approximate to 5MeV and tentative spin-parity assignments up to I-pi = 18(+). Linear polarization and angular distribution measurements were used to determine the electromagnetic E1 character of the dipole transitions connecting the positive-parity ground-state band with an excited side-band, firmly establishing it as a negativeparity band. The lowestmember of this negative-parity structure was firmly assigned spin-parity 3(-). In addition, we observed an E3 transition from this 3(-) state to the ground state, providing direct evidence for octupole collectivity in Pt-172. Large-scale shell model (LSSM) and total Routhian surface (TRS) calculations have been performed, supporting the interpretation of the 3(-) state as a collective octupole-vibrational state.

Place, publisher, year, edition, pages
SPRINGER, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-271288 (URN)10.1140/epja/s10050-020-00071-6 (DOI)000517208400001 ()2-s2.0-85079637616 (Scopus ID)
Note

QC 20200402

Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2020-05-11Bibliographically approved
Ertoprak, A., Cederwall, B., Qi, C., Aktas, Ö., Doncel, M., Hadinia, B., . . . Wyss, R. A. (2020). Evidence for octupole collectivity in 172Pt. European Physical Journal A, 56(65)
Open this publication in new window or tab >>Evidence for octupole collectivity in 172Pt
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2020 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 56, no 65Article in journal (Refereed) Published
Abstract [en]

Excited states in the extremely neutron-deficient nucleus 172Pt were populated via 96Ru(78Kr,2p) and 92Mo(83Kr,3n) reactions. The level scheme has been extended up to an excitation energy of  ~ 5 MeV and tentative spin-parity assignments up to Iπ = 18+. Linear polarization and angular distribution measurements were used to determine the electromagnetic E1 character of the dipole transitions connecting the positive-parity ground-state band with an excited side-band, firmly establishing it as a negative-parity band. The lowest member of this negative-parity structure was firmly assigned spin-parity 3-. In addition, we observed an E3 transition from this 3- state to the ground state, providing direct evidence for octupole collectivity in 172Pt. Large-scale shell model (LSSM) and total Routhian surface (TRS) calculations have been performed, supporting the interpretation of the 3- state as a collective octupole-vibrational state.

Place, publisher, year, edition, pages
Springer, 2020
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-271657 (URN)10.1140/epja/s10050-020-00071-6 (DOI)2-s2.0-85079637616 (Scopus ID)
Funder
Swedish Research Council, 621-2014-5558
Note

QC 20200427

Available from: 2020-04-03 Created: 2020-04-03 Last updated: 2020-05-11Bibliographically approved
Sun, M. D., Liu, Z., Qi, C., Zhang, F. S. & et al., . (2020). Fine structure in the alpha decay of U-223. Physics Letters B, 800, Article ID 135096.
Open this publication in new window or tab >>Fine structure in the alpha decay of U-223
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2020 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 800, article id 135096Article in journal (Refereed) Published
Abstract [en]

Fine structure in the alpha decay of U-223 was observed in the fusion-evaporation reaction Re-187(Ar-40, p3n) by using fast digital pulse processing technique. Two alpha-decay branches of U-223 feeding the ground state and 244 keV excited state of Th-219 were identified by establishing the decay chain U-223 (alpha(1)) under right arrow Th-219 (alpha(2)) under right arrow Ra-215 (alpha(3)) under right arrow Rn-211. The alpha-particle energy for the ground-state to ground-state transition of U-223 was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62(-10)(+14) mu s. Evolution of nuclear structure for N = 131 even-Z isotones from Po to U was discussed in the frameworks of nuclear mass and reduced alpha-decay width, a weakening octupole deformation in the ground state of U-223 relative to its lighter isotones Ra-219 and Th-221 was suggested.

Place, publisher, year, edition, pages
ELSEVIER, 2020
Keywords
Fine structure, alpha decay, Spin and parity, Reduced alpha-decay width, Quadrupole-octupole deformation
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-266928 (URN)10.1016/j.physletb.2019.135096 (DOI)000503832500021 ()2-s2.0-85075219606 (Scopus ID)
Note

QC 20200203

Available from: 2020-02-03 Created: 2020-02-03 Last updated: 2020-02-03Bibliographically approved
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 ()2-s2.0-85065158288 (Scopus ID)
Note

QC 20190327

Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2020-03-09Bibliographically 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
Wang, Y.-Z., Su, X.-D., Qi, C. & Gu, J.-Z. (2019). Tensor force effect on the exotic structure of neutron-rich Ca isotopes*. Chinese Physics C, High Energy Physics & Nuclear Physics, 43(11), Article ID 114101.
Open this publication in new window or tab >>Tensor force effect on the exotic structure of neutron-rich Ca isotopes*
2019 (English)In: Chinese Physics C, High Energy Physics & Nuclear Physics, ISSN 1674-1137, E-ISSN 0899-9996, Vol. 43, no 11, article id 114101Article in journal (Refereed) Published
Abstract [en]

The structure of neutron-rich Ca isotopes is studied in the spherical Skyrme-Hartree-Fock-Bogoliubov (SHFB) approach with SLy5, SLy5+T, and 36 sets of TIJ parametrizations. The calculated results are compared with the available experimental data for the average binding energies, two-neutron separation energies and charge radii. It is found that the SLy5+T, T31, and T32 parametrizations reproduce best the experimental properties, especially the neutron shell effects at N = 20, 28 and 32, and the recently measured two-neutron separation energy of Ca-56. The calculations with the SLy5+T and T31 parametrizations are extended to isotopes near the neutron drip line. The neutron giant halo structure in the very neutron-rich Ca isotopes is not seen with these two interactions. However, depleted neutron central densities are found in these nuclei. By analyzing the neutron mean-potential, the reason for the bubble-like structure formation is given.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
spherical SHFB approach, tensor force, neutron-rich Ca isotopes, neutron giant halo, bubble structure
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-264159 (URN)10.1088/1674-1137/43/11/114101 (DOI)000493109100002 ()2-s2.0-85076024773 (Scopus ID)
Note

QC 20191210

Available from: 2019-12-10 Created: 2019-12-10 Last updated: 2020-01-10Bibliographically 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: 2020-04-07Bibliographically 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
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1406-5695

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