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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: 2020-04-02Bibliographically 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)
Funder
Swedish Research Council, 621-2014-5558
Available from: 2020-04-03 Created: 2020-04-03 Last updated: 2020-04-03
Ciemala, M., Atac Nyberg, A., Cederwall, B. & Simonis, J. (2020). Testing ab initio nuclear structure in neutron-rich nuclei: Lifetime measurements of second 2(+) state in C-16 and O-20. Physical Review C: Covering Nuclear Physics, 101(2), Article ID 021303.
Open this publication in new window or tab >>Testing ab initio nuclear structure in neutron-rich nuclei: Lifetime measurements of second 2(+) state in C-16 and O-20
2020 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 101, no 2, article id 021303Article in journal (Refereed) Published
Abstract [en]

To test the predictive power of ab initio nuclear structure theory, the lifetime of the second 2(+) state in neutron-rich O-20, tau(2(2)(+)) = 150(-30)(+80) fs, and an estimate for the lifetime of the second 2(+) state in C-16 have been obtained for the first time. The results were achieved via a novel Monte Carlo technique that allowed us to measure nuclear state lifetimes in the tens-to-hundreds of femtoseconds range by analyzing the Doppler-shifted gamma-transition line shapes of products of low-energy transfer and deep-inelastic processes in the reaction O-18 (7.0 MeV/u) + Ta-181. The requested sensitivity could only be reached owing to the excellent performances of the Advanced gamma-Tracking Array AGATA, coupled to the PARIS scintillator array and to the VAMOS++ magnetic spectrometer. The experimental lifetimes agree with predictions of ab initio calculations using two- and three-nucleon interactions, obtained with the valence-space in-medium similarity renormalization group for O-20 and with the no-core shell model for C-16. The present measurement shows the power of electromagnetic observables, determined with high-precision gamma spectroscopy, to assess the quality of first-principles nuclear structure calculations, complementing common benchmarks based on nuclear energies. The proposed experimental approach will be essential for short lifetime measurements in unexplored regions of the nuclear chart, including r-process nuclei, when intense beams, produced by Isotope Separation On-Line (ISOL) techniques, become available.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-271283 (URN)10.1103/PhysRevC.101.021303 (DOI)000517222700001 ()
Note

QC 20200331

Available from: 2020-03-31 Created: 2020-03-31 Last updated: 2020-03-31Bibliographically approved
Lv, B. F., Petrache, C. M., Chen, Q. B., Meng, J., Astier, A., Dupon, E., . . . Andreoiu, C. (2019). Chirality of Nd-135 reexamined: Evidence for multiple chiral doublet bands. Physical Review C: Covering Nuclear Physics, 100(2), Article ID 024314.
Open this publication in new window or tab >>Chirality of Nd-135 reexamined: Evidence for multiple chiral doublet bands
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2019 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 100, no 2, article id 024314Article in journal (Refereed) Published
Abstract [en]

One new pair of positive-parity chiral doublet bands have been identified in the odd-A nucleus Nd-135 which together with the previously reported negative-parity chiral doublet bands constitute a third case of multiple chiral doublet (M chi D) bands in the A approximate to 130 mass region. The properties of the M chi D bands are well reproduced by constrained covariant density functional theory and particle rotor model calculations. The newly observed M chi D bands in Nd-135 represents an important milestone in supporting the existence of M chi D in nuclei.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-257444 (URN)10.1103/PhysRevC.100.024314 (DOI)000480389500002 ()2-s2.0-85070893337 (Scopus ID)
Note

QC 20190903

Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-03Bibliographically approved
Petrache, C. M., Frauendorf, S., Lv, B. F., Astier, A., Dupont, E., Guo, S., . . . Andreoiu, C. (2019). Collective rotation of an oblate nucleus at very high spin. Physical Review C: Covering Nuclear Physics, 99(4), Article ID 041301.
Open this publication in new window or tab >>Collective rotation of an oblate nucleus at very high spin
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2019 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 99, no 4, article id 041301Article in journal (Refereed) Published
Abstract [en]

A sequence of nine almost equidistant quadrupole transitions is observed in Nd-137. The sequence represents an extremely regular rotational band that extends to a spin of about 75/2 and an excitation energy of approximate to 4.5 MeV above yrast. Cranked mean-field calculations of the Nilsson-Strutinsky type suggest an oblate shape for the band. They reproduce the observed I(I +1) dependence of the rotational energy whereas predicting a pronounced decrease in the deformation, which is the hallmark of antimagnetic rotation.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-249862 (URN)10.1103/PhysRevC.99.041301 (DOI)000462906600001 ()2-s2.0-85064077764 (Scopus ID)
Note

QC 20190426

Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-04-26Bibliographically approved
Petrache, C. M., Wyss, R. A., Back, T., Cederwall, B. & Tucholski, A. (2019). Diversity of shapes and rotations in the gamma-soft Ba-130 nucleus: First observation of a t-band in the A=130 mass region. PHYSICS LETTERS B, 795, 241-247
Open this publication in new window or tab >>Diversity of shapes and rotations in the gamma-soft Ba-130 nucleus: First observation of a t-band in the A=130 mass region
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2019 (English)In: PHYSICS LETTERS B, Vol. 795, p. 241-247Article in journal (Refereed) Published
Abstract [en]

Several new bands have been identified in Ba-130, among which there is one with band-head spin 8(+). Its properties are in agreement with the Fermi-aligned nu h(11/2)(2)[523]circle times 9/2(-)[514] Nilsson configuration. This is the first observation of a two-quasiparticle t-band in the A = 130 mass region. The t-band is fed by a dipole band involving two additional h(11/2) protons. The odd-spin partners of the proton and neutron S-bands and the ground-state band at high spins are also newly identified. The observed bands are discussed using several theoretical models, total Routhians surfaces (TRS), tilted axis cranking (TAC), particle rotor model (PRM) and projected shell model (PSM), which strongly suggest the coexistence of prolate and oblate shapes polarized by rotation aligned two-proton and two-neutron configurations, as well as prolate collective rotations around axes with different orientations. With the new results, 130 Ba presents one of the best and most complete sets of collective excitations that a gamma-soft nucleus can manifest at medium and high spins, revealing a diversity of shapes and rotations for the nuclei in the A = 130 mass region.

Place, publisher, year, edition, pages
ELSEVIER, 2019
Keywords
Nuclear structure, Collective rotations, Shape coexistence, Particle rotor model, Projected shell model, Tiltid axis cranking
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-256247 (URN)10.1016/j.physletb.2019.06.040 (DOI)000477924000034 ()2-s2.0-85067816517 (Scopus ID)
Note

QC 20191022

Available from: 2019-10-22 Created: 2019-10-22 Last updated: 2019-10-22Bibliographically approved
Ralet, D., Cederwall, B. & Wieland, O. (2019). Evidence of octupole-phonons at high spin in Pb-207. Physics Letters B, 797, Article ID UNSP 134797.
Open this publication in new window or tab >>Evidence of octupole-phonons at high spin in Pb-207
2019 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 797, article id UNSP 134797Article in journal (Refereed) Published
Abstract [en]

A lifetime measurement of the 19/2(-) state in Pb-207 has been performed using the Recoil Distance Doppler-Shift (RDDS) method. The nuclei of interest were produced in multi-nucleon transfer reactions induced by a Pb-208 beam impinging on a Mo-100 enriched target. The beam-like nuclei were detected and identified in terms of their atomic mass number in the VAMOS++ spectrometer while the prompt gamma rays were detected by the AGATA tracking array. The measured large reduced transition probability B(E3, 19/2(-) -> 13/2(+)) = 40(8) W.u. is the first indication of the octupole phonon at high spin in Pb-207. An analysis in terms of a particle-octupole-vibration coupling model indicates that the measured B(E3) value in Pb-207 is compatible with the contributions from single-phonon and single particle E3 as well as E3 strength arising from the double-octupole-phonon 6(+) state, all adding coherently. A crucial aspect of the coupling model, namely the strong mixing between single-hole and the phonon-hole states, is confirmed in a realistic shell-model calculation. Crown Copyright B.V.

Place, publisher, year, edition, pages
ELSEVIER, 2019
Keywords
AGATA spectrometer, gamma-Ray tracking, VAMOS plus plus spectrometer, Plunger device, Nuclear deformation, Octupole phonon
National Category
Physical Sciences
Research subject
Physics, Atomic, Subatomic and Astrophysics
Identifiers
urn:nbn:se:kth:diva-262773 (URN)10.1016/j.physletb.2019.134797 (DOI)000488071200015 ()2-s2.0-85069864523 (Scopus ID)
Note

QC 20191022

Available from: 2019-10-22 Created: 2019-10-22 Last updated: 2019-11-26Bibliographically approved
Trombetta, D. M., Klintefjord, M., Axell, K. & Cederwall, B. (2019). Fast neutron- and γ-ray coincidence detection for nuclear security and safeguards applications. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 927, 119-124
Open this publication in new window or tab >>Fast neutron- and γ-ray coincidence detection for nuclear security and safeguards applications
2019 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 927, p. 119-124Article in journal (Refereed) Published
Abstract [en]

The use of passive and active interrogation techniques to evaluate materials concerning their content of special nuclear materials (SNM) is fundamental in fields such as nuclear safeguards and security. Detection of fast neutrons and γ rays, which are a characteristic signature of SNM, has several potential advantages compared with the commonly used systems based on thermal and epithermal neutron counters, the most important being the much shorter required coincidence times and the correspondingly reduced rate of background events due to accidental coincidences. Organic scintillators are well suited for this purpose due to their fast timing properties and composition being based on carbon and hydrogen with large elastic scattering cross-sections for fast neutrons. Organic scintillators also have suitable detection efficiency for γ rays and exhibit pulse shape properties which are favorable for distinguishing between neutrons and γ rays. This paper presents experimental results and Monte Carlo simulations for a neutron–neutron and γ-neutron coincidence detection setup for identification and characterization of SNM based on such detectors. The measurements were carried out on different samples of PuO 2 material with varying content of 240 Pu at the Joint Research Center (JRC) of the European Commission, Ispra, Italy. The results demonstrate significant advantages of fast neutron-γ coincidence detection over fast neutron–neutron coincidence counting for certain applications, e.g. for nuclear security systems, even in the presence of moderate amounts of shielding.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Fast neutron and gamma detection, Monte Carlo simulations, Non-destructive analysis (NDA), Nuclear safeguards, Nuclear security, Organic liquid scintillator detector
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-246418 (URN)10.1016/j.nima.2019.01.081 (DOI)000462142700014 ()2-s2.0-85061781911 (Scopus ID)
Note

QC 20190319

Available from: 2019-03-19 Created: 2019-03-19 Last updated: 2019-04-24Bibliographically approved
Petrache, C. M., Cederwall, B., Aktas, Ö., Ertoprak, A., Liu, H., Andreoiu, C. & et al., . (2019). Highly deformed bands in Nd nuclei: New results and consistent interpretation within the cranked Nilsson-Strutinsky formalism. Physical Review C: Covering Nuclear Physics, 100(5), Article ID 054319.
Open this publication in new window or tab >>Highly deformed bands in Nd nuclei: New results and consistent interpretation within the cranked Nilsson-Strutinsky formalism
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2019 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 100, no 5, article id 054319Article in journal (Refereed) Published
Abstract [en]

Three new highly-deformed (HD) bands are identified in Nd-136 and the highly deformed band of Nd-137 is extended at higher spin by four transitions, revealing a band crossing associated with the occupation of the second nu i(13/2 )intruder orbital. Extended cranked Nilsson-Strutinsky calculations are performed for all HD bands observed in Nd-134, Nd-136, and Nd-137, achieving for the first time a consistent interpretation of all HD bands in the Nd nuclei. The new interpretation has significant consequences, like the change of parity of the yrast HD bands of Nd-134 and Nd-136, and the involvement of two negative-parity neutron intruder orbitals in the configurations of most HD bands. The present experimental results and their theoretical interpretation represent an important step forward in the understanding of the second-minimum excitations in the Nd nuclei.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-264901 (URN)10.1103/PhysRevC.100.054319 (DOI)000496741800003 ()2-s2.0-85075787062 (Scopus ID)
Note

QC 20191219

Available from: 2019-12-19 Created: 2019-12-19 Last updated: 2019-12-19Bibliographically approved
Qiang, Y. H., Cederwall, B. & Xu, F. R. (2019). Identification of high-K rotation in Ba-130: Testing the consistency of electromagnetic observables. Physical Review C: Covering Nuclear Physics, 99(1), Article ID 014307.
Open this publication in new window or tab >>Identification of high-K rotation in Ba-130: Testing the consistency of electromagnetic observables
2019 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 99, no 1, article id 014307Article in journal (Refereed) Published
Abstract [en]

The band built on the K-pi = 8(-), T-1/2 = 9.4 ms isomer of( 130)Ba has been identified, filling the gap in the systematics of the dipole bands built on the 8(- )isomers in the N = 74 isotones from( 128)Xe to Gd-138. The use of the GALILEO array in conjunction with its ancillaries EUCLIDES and Neutron Wall, helped to firmly place the newly identified transitions on top of the long-lived isomer. The extracted g(K)and g(R) gyromagnetic factors are in agreement with the 7/2(+)[404] circle times 9/2(-)[514] two-neutron Nilsson configuration. Particle-rotor model calculations give an understanding of the limited degree of K mixing. The experimental information on the K-pi = 8(-) isomer of Ba-130 is now the most complete among the K isomers of the N = 74 isotones.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-242243 (URN)10.1103/PhysRevC.99.014307 (DOI)000455164000003 ()2-s2.0-85059834023 (Scopus ID)
Note

QC 20190129

Available from: 2019-01-29 Created: 2019-01-29 Last updated: 2019-08-06Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1771-2656

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