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Sökning: WFRF:(Andreoiu C.)

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1.
  • Delafosse, C., et al. (författare)
  • Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni-78 Region : A Hint from Lifetime Measurements
  • 2018
  • Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:19
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetime measurements of excited states of the light N = 52 isotones Kr-88, Se-86, and Ge-84 have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B(E2; 2(+)-> 0(+)) and B(E2; 4(+)-> 2(+)) were obtained for the first time for the hard-to-reach 84Ge. While the B(E2; 2(+)-> 0(+) ) values of Kr-88, Se-86 saturate the maximum quadrupole collectivity offered by the natural valence (3s, 2d, 1g(7/2), 1h(11/2)) space of an inert Ni-78 core, the value obtained for Ge-84 largely exceeds it, suggesting that shape coexistence phenomena, previously reported at N less than or similar to 49, extend beyond N = 50. The onset of collectivity at Z = 32 is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector rho field in shell-structure evolution.
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2.
  • Andersson, Lise-Lotte, et al. (författare)
  • Extensive Gamma-ray Spectroscopy of Normally and Superdeformed Structures in 61Cu
  • 2008
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 36:3, s. 251-278
  • Tidskriftsartikel (refereegranskat)abstract
    • A largely extended experimental knowledge of the Cu-61(29)32 nucleus has been obtained from three experiments. Excited states in Cu-61 were produced via the fusion-evaporation reaction Si-28(Ar-36, 3p)Cu-61. In addition to the Ge array GAMMASPHERE, neutron and charged-particle detectors placed around the target position were used for high-performance particle spectroscopy. The constructed level scheme includes more than 160 energy levels and 320 gamma-ray transitions belonging to both normally deformed as well as superdeformed rotational structures. The multipolarities have been determined for the gamma-ray transitions and as a result spin-parity assignments are given for nearly all energy levels. Experimental results in the normally deformed region are compared with predictions from large-scale shell model calculations. The collective structures are compared with results from cranked Nilsson-Strutinsky calculations. The results reveal the need to modify the standard Nilsson parameters in the mass A similar to 60 region.
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3.
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4.
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5.
  • Gellanki, Jnaneswari, et al. (författare)
  • Characterization of Superdeformed Bands in 62Zn
  • 2009
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Combined data from four fusion-evaporation reaction experiments were utilized to investigate deformed and superdeformed structures in Zn-62(30)32. Combination of the Gammasphere gamma-ray spectrometer and ancillary particle detection systems allowed for the connection of rotational bands to well-known, low-lying excited states in Zn-62, as well as spectroscopy of discrete high-spin states reaching excitation energies of E-x=42.5 MeV. Four well- or superdeformed bands in Zn-62 are characterized and described by means of cranked Nilsson-Strutinsky calculations.
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6.
  • Johansson, Emma, et al. (författare)
  • Prompt Proton Decay and Deformed Bands in 56Ni
  • 2008
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 77:6
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in the doubly magic N=Z nucleus Ni-56 have been investigated with three fusion-evaporation reaction experiments. New gamma-ray transitions are added, and a confirmation of a previously suggested prompt proton decay from a rotational band in Ni-56 into the ground state of Co-55 is presented. The rotational bands in Ni-56 are discussed within the framework of cranked Nilsson-Strutinsky calculations.
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7.
  • Torres, D. A., et al. (författare)
  • Deformations and Magnetic Rotations in the 60Ni Nucleus
  • 2008
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 78:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Data from three experiments using the heavy-ion fusion evaporation-reaction Ar-36+Si-28 have been combined to study high-spin states in the residual nucleus Ni-60, which is populated via the evaporation of four protons from the compound nucleus Ge-64. The GAMMASPHERE array was used for all the experiments in conjunction with a 4 pi charged-particle detector arrays (MICROBALL, LUWUSIA) and neutron detectors (NEUTRON SHELL) to allow for the detection of. rays in coincidence with the evaporated particles. An extended Ni-60 level scheme is presented, comprising more than 270 gamma-ray transitions and 110 excited states. Their spins and parities have been assigned via directional correlations of gamma rays emitted from oriented states. Spherical shell-model calculations in the fp-shell characterize some of the low-spin states, while the experimental results of the rotational bands are analyzed with configuration-dependent cranked Nilsson-Strutinsky calculations.
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8.
  • Andreoiu, Corina, et al. (författare)
  • Yrast Superdeformed Band in 59Cu
  • 2000
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 62:5, s. 513011-513015
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in 59Cu were populated using the fusion-evaporation reactions 28Si+40Ca at a beam energy of 125 MeV and 36Ar+28Si at a beam energy of 143 MeV. The Gammasphere array in conjunction with ancillary detector systems allowed for the identification of a superdeformed rotational band in 59Cu, which was firmly linked to low-spin yrast states. Using directional correlations of oriented states, a spin-parity assignment of Iπ = 25/2+ to the band head was possible. The average quadrupole moment of the band is measured to be Qt = (2.24±0.40) e b. The characteristics of the band are compared to neighboring nuclei and predictions of different mean-field theories.
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9.
  • Henderson, J., et al. (författare)
  • Coulomb excitation of the vertical bar T-z vertical bar=1/2, A=23 mirror pair
  • 2022
  • Ingår i: PHYSICAL REVIEW C. - 2469-9985 .- 2469-9993. ; 105:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Electric-quadrupole (E2) strengths relate to the underlying quadrupole deformation of a nucleus and present a challenge for many nuclear theories. Mirror nuclei in the vicinity of the line of N = Z represent a convenient laboratory for testing deficiencies in such models, making use of the isospin symmetry of the systems. Purpose: Uncertainties associated with literature E2 strengths in Mg-23 are some of the largest in T-z = vertical bar 1/2 vertical bar nuclei in the sd shell. The purpose of the present paper is to improve the precision with which these values are known, to enable better comparison with theoretical models. Methods: Coulomb-excitation measurements of Mg-23 and Na-23 were performed at the TRIUMF-ISAC facility using the TIGRESS spectrometer. They were used to determine the E2 matrix elements of mixed E2/M1 transitions. Results: Reduced E2 transition strengths, B(E2), were extracted for Mg-23 and Na-23. Their precision was improved by factors of approximately 6 for both isotopes, while agreeing within uncertainties with previous measurements. Conclusions: A comparison was made with both shell-model and ab initio valence-space in-medium similarity renormalization group calculations. Valence-space in-medium similarity renormalization group calculations were found to underpredict the absolute E2 strength, in agreement with previous studies.
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10.
  • Johansson, Emma, et al. (författare)
  • Thorough Gamma-ray and Particle Decay Investigations of 58Ni
  • 2009
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The combined data from three fusion-evaporation reaction experiments have been utilized to investigate the semi-magic nucleus Ni-58(28)30. To detect gamma rays in coincidence with evaporated particles, the Ge-detector array Gammasphere was used in conjunction with the charged-particle detectors Microball and LuWuSiA (the Lund Washington University Silicon Array), and a neutron detector array. The results yield a significantly extended level scheme of Ni-58 comprising some 340 gamma-ray transitions and include a total of at least 14 discrete particle decays into excited states of the daughter nuclei Fe-54 and Co-57. The level scheme is compared with large-scale shell-model calculations and cranked Nilsson-Strutinsky calculations.
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11.
  • Moukaddam, M., et al. (författare)
  • In-beam internal conversion electron spectroscopy with the SPICE detector
  • 2018
  • Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 905, s. 180-187
  • Tidskriftsartikel (refereegranskat)abstract
    • The SPectrometer for Internal Conversion Electrons (SPICE) has been commissioned for use in conjunction with the TIGRESS γ-ray spectrometer at TRIUMF's ISAC-II facility. SPICE features a permanent rare-earth magnetic lens to collect and direct internal conversion electrons emitted from nuclear reactions to a thick, highly segmented, lithium-drifted silicon detector. This arrangement, combined with TIGRESS, enables in-beam γ-ray and internal conversion electron spectroscopy to be performed with stable and radioactive ion beams. Technical aspects of the device, capabilities, and initial performance are presented.
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12.
  • Paul, E. S., et al. (författare)
  • The highest spin discrete levels in Ce-131,Ce-132
  • 2006
  • Ingår i: Physica Scripta. - 0031-8949. ; T125, s. 115-118
  • Tidskriftsartikel (refereegranskat)abstract
    • The three superdeformed (SD) bands in Ce-132 and the two SD bands in Ce-131 have been extended to higher spin following experiments with the EUROBALL IV spectrometer. The two SD bands in 131Ce have been linked together. However, despite the relatively high population intensity of the bands ( up to 5% of the respective channel), it has not been possible to unambiguously link any of the five SD bands into the low-spin, normally deformed structures of Ce-131,Ce-132.
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13.
  • Dunlop, R., et al. (författare)
  • β decay and β-delayed neutron decay of the N=82 nucleus 13149In82
  • 2019
  • Ingår i: Physical Review C: covering nuclear physics. - 2469-9985.
  • Tidskriftsartikel (refereegranskat)abstract
    • The half-lives of three β-decaying states of 13149In82 have been measured with the GRIFFIN γ-ray spectrometer at the TRIUMF-ISAC facility to be T1/2(1/2−)=328(15)ms, T1/2(9/2+)=265(8)ms, and T1/2(21/2+)=323(55)ms, respectively. The first observation of γ rays following the βn decay of 131In into 130Sn is reported. The β-delayed neutron emission probability is determined to be P1n=12(7)% for the 21/2+ state and 2.3(3)% from the combined 1/2− and 9/2+ states of 13149In82 observed in this experiment. A significant expansion of the decay scheme of 131In, including 17 new excited states and 35 new γ-ray transitions in 13150Sn81 is also reported. This leads to large changes in the deduced β-branching ratios to some of the low-lying states of 131Sn compared to previous work with implications for the strength of the first-forbidden β transitions in the vicinity of doubly magic 13250Sn82.
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14.
  • Jigmeddorj, B., et al. (författare)
  • New low-spin states of 122Xe observed via high-statistics beta-decay of 122Cs
  • 2018
  • Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2100-014X. ; 178, s. 02026-02026
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states of 122Xe were studied via the β+/EC decay of 122Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. Compton-suppressed HPGe detectors were used for measurements of γ-ray intensities, γγ coincidences, and γ-γ angular correlations. Two sets of data were collected to optimize the decays of the ground (21.2 s) and isomeric (3.7 min) states of 122Cs. The data collected have enabled the observation of about 505 new transitions and about 250 new levels, including 51 new low-spin states. Spin assignments have been made for 58 low-spin states based on the deduced β-decay feeding and γ-γ angular correlation analyses.
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15.
  • Lv, B. F., et al. (författare)
  • Chirality of Nd-135 reexamined : Evidence for multiple chiral doublet bands
  • 2019
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 100:2
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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16.
  • Lv, B. F., et al. (författare)
  • Evidence against the wobbling nature of low-spin bands in 135Pr
  • 2022
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 824
  • Tidskriftsartikel (refereegranskat)abstract
    • The electromagnetic character of the ΔI=1 transitions connecting the 1- to 0-phonon and the 2- to 1-phonon wobbling bands should be dominated by an E2 component, due to the collective motion of the entire nuclear charge. In the present work it is shown, based on combined angular correlation and linear polarization measurements, that the mixing ratios of all analyzed connecting transitions between low-lying bands in 135Pr interpreted as 0-, 1-, and 2-phonon wobbling bands, have absolute values smaller than one. This indicates predominant M1 magnetic character, which is incompatible with the proposed wobbling nature. All experimental observables are instead in good agreement with quasiparticle-plus-triaxial-rotor model calculations, which describe the bands as resulting from a rapid re-alignment of the total angular momentum from the short to the intermediate nuclear axis.
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17.
  • Lv, B. F., et al. (författare)
  • Evolution from γ -soft to stable triaxiality in Nd 136 as a prerequisite of chirality
  • 2018
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 98:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The level structure of Nd136 has been investigated using the Mo100(Ar40,4n) reaction and the JUROGAM II+RITU+GREAT setup. The level scheme has been extended significantly. Many new bands have been identified both at low and high spin, among which are five nearly degenerate bands interpreted as chiral partners. Excitation energies, spins, and parities of the previously known bands are revised and firmly established, and some previously known bands have been revised. Configurations are assigned to the observed bands based on cranked Nilsson-Strutinsky calculations. The band structure of Nd136 is now clarified and the various types of single-particle and collective excitations are well understood.
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18.
  • Lv, B. F., et al. (författare)
  • Tilted precession bands in Nd 135
  • 2021
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 103:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new excited bands built on the πh11/2 configuration have been identified in Nd135 in addition to the known πh11/2 band. The energy spectra of the excited bands and the available electromagnetic transition probabilities are in good agreement with theoretical results obtained using quasiparticle-plus-triaxial-rotor model calculations. The properties of the bands identify them as tilted precession bands instead of wobbling bands. Our results give a new insight into the interpretation of the low-lying bands in odd-A mass nuclei, and can stimulate future studies to address the nuclear triaxiality.
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19.
  • Petrache, C. M., et al. (författare)
  • Collective rotation of an oblate nucleus at very high spin
  • 2019
  • Ingår i: Physical Review C. - : American Physical Society (APS). - 2469-9985 .- 2469-9993. ; 99:4
  • Tidskriftsartikel (refereegranskat)abstract
    • A sequence of nine almost equidistant quadrupole transitions is observed in Nd137. The sequence represents an extremely regular rotational band that extends to a spin of about 75/2 and an excitation energy of ≈4.5MeV 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. 
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20.
  • Petrache, C. M., et al. (författare)
  • Evidence of chiral bands in even-even nuclei
  • 2018
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 97:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Evidence for chiral doublet bands has been observed for the first time in the even-even nucleus Nd136. One chiral band was firmly established. Four other candidates for chiral bands were also identified, which can contribute to the realization of the multiple pairs of chiral doublet bands (MχD) phenomenon. The observed bands are investigated by the constrained and tilted axis cranking covariant density functional theory (TAC-CDFT). Possible configurations have been explored. The experimental energy spectra, angular momenta, and B(M1)/B(E2) values for the assigned configurations are globally reproduced by TAC-CDFT. Calculated results support the chiral interpretation of the observed bands, which correspond to shapes with maximum triaxiality induced by different multiquasiparticle configurations in Nd136.
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21.
  • Petrache, C. M., et al. (författare)
  • Highly deformed bands in Nd nuclei : New results and consistent interpretation within the cranked Nilsson-Strutinsky formalism
  • 2019
  • Ingår i: Physical Review C. - : American Physical Society (APS). - 2469-9985 .- 2469-9993. ; 100:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Three new highly-deformed (HD) bands are identified in Nd136 and the highly deformed band of Nd137 is extended at higher spin by four transitions, revealing a band crossing associated with the occupation of the second νi13/2 intruder orbital. Extended cranked Nilsson-Strutinsky calculations are performed for all HD bands observed in Nd134, Nd136, and Nd137, 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 Nd134 and Nd136, 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.
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22.
  • Petrache, C. M., et al. (författare)
  • Multiple chiral bands in 137 Nd
  • 2020
  • Ingår i: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 56:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new bands have been identified in 137Nd from a high-statistics JUROGAM II gamma-ray spectroscopy experiment. Constrained density functional theory and particle rotor model calculations are used to assign configurations and investigate the band properties, which are well described and understood. It is demonstrated that these two new bands can be interpreted as chiral partners of previously known three-quasiparticle positive- and negative-parity bands. The newly observed chiral doublet bands in 137Nd represent an important support to the existence of multiple chiral bands in nuclei. The present results constitute the missing stone in the series of Nd nuclei showing multiple chiral bands, which becomes the most extended sequence of odd–even and even-even nuclei presenting multiple chiral bands in the Segré chart.
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23.
  • Petrache, C. M., et al. (författare)
  • Signatures of enhanced octupole correlations at high spin in Nd 136
  • 2020
  • Ingår i: Physical Review C. - : American Physical Society (APS). - 2469-9985 .- 2469-9993. ; 102:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Experimental signatures of moderately enhanced octupole correlations at high spin in Nd136 are indicated for the first time. The extracted dipole moments of two negative-parity bands are only two times smaller than those of the lanthanide nuclei with N≈90 which present well-established octupole correlations. Calculations using the cranked quasiparticle random phase approximation and a model of quadrupole-octupole rotations with octupole vibrations reveal the structure of the bands and the enhanced octupole correlations at high spin in Nd136.
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24.
  • Rudolph, D., et al. (författare)
  • Low-, medium-, and high-spin states in the N=Z+1 nucleus 63Ga
  • 2021
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 103:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The fusion-evaporation reaction 28Si+40Ca at 122 MeV beam energy was used to populate excited states in the N=Z+1 nucleus 63Ga. With the combination of the Gammasphere spectrometer and the Microball CsI(Tl) charged-particle detector array, the level scheme of 63Ga was extended by more than a factor of two in terms of number of γ-ray transitions and excited states, excitation energy (Ex>30 MeV), and angular momentum (I>30 ℏ). Nine regular sequences of states were newly established in the high-spin part of the level scheme. The majority of these rotational band structures could be connected to the previously known part of the level scheme by high-energy γ-ray transitions in the energy range Eγ=4–6 MeV. Low-spin states were assessed by shell-model calculations. The high-spin rotational bands were interpreted and classified by means of cranked Nilsson-Strutinsky calculations.
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25.
  • Rudolph, D., et al. (författare)
  • Onset of high-spin rotational bands in the N=Z nucleus 62Ga
  • 2020
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985. ; 102:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The fusion-evaporation reaction 28Si + 40Ca at 122 MeV beam energy was used to populate high-spin states in the odd-odd N = Z nucleus 62Ga. With the combination of the Gammasphere spectrometer and the Microball CsI(Tl) charged-particle detector array the decay scheme of 62Ga was extended beyond 10 MeV excitation energy. The onset of band structures was observed. These high-spin rotational states are interpreted and classified by means of cranked Nilsson-Strutinsky calculations.
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26.
  • Andersson, Lise-Lotte, et al. (författare)
  • Comprehensive Gamma-ray Spectroscopy of Rotational Bands in the N=Z+1 Nucleus 61Zn
  • 2009
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 79:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The Zn-61(30)31 nucleus has been studied via the combined data of two fusion-evaporation reaction experiments using a Ar-36 beam and a Si-28 target foil. The experimental setups involved the Ge array GAMMASPHERE and neutron and charged particle detectors placed around the target position. The resulting level scheme comprises about 120 excited states connected via some 180 gamma-ray transitions. In total, seven rotational structures were identified up to I similar to 25 or higher and compared with predictions from cranked Nilsson-Strutinsky calculations.
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27.
  • Andreoiu, Corina, et al. (författare)
  • First Identification of Excited States in 59Zn
  • 2002
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 15, s. 459-462
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in 59Zn were observed for the first time following the fusion-evaporation reaction 24Mg + 40Ca at a beam energy of 60 MeV. The GASP array in conjunction with the ISIS Silicon ball and the NeutronRing allowed for the detection of n-rays in coincidence with evaporated light particles. The mirror symmetry of 59Zn and 59Cu is discussed.
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28.
  • du Rietz, Rickard, et al. (författare)
  • Investigation of High-spin States in 53Fe
  • 2005
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 72:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The fusion-evaporation reactions Si-28(S-32,1 alpha 2p1n)Fe-53 at 125 MeV and Mg-24(S-32,2p1n)Fe-53 at a 95-MeV beam energy were used to investigate excited states in Fe-53. The combination of the Gammasphere Ge detector array and ancillary devices led to the construction of an extensive level scheme comprising some 90 transitions connecting 40 states. The lifetime of the yrast 25/2(-) state and upper limits for the lifetimes of a number of additional states were determined using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The experimental results are compared to large-scale shell-model calculations using different sets of two-body matrix elements. In particular, predictions on electromagnetic decay properties such as lifetimes, branching ratios, and mixing ratios are studied in detail.
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29.
  • Gadea, A., et al. (författare)
  • Observation of Ni-54 : Cross-conjugate symmetry in f(7/2) mirror energy differences
  • 2006
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:15, s. 152501-
  • Tidskriftsartikel (refereegranskat)abstract
    • Gamma decays from excited states up to J(pi)=6(+) in the N=Z-2 nucleus Ni-54 have been identified for the first time. Level energies are compared with those of the isobars Co-54 and Fe-54 and of the cross-conjugate nuclei of mass A=42. The good but puzzling f(7/2) cross-conjugate symmetry in mirror and triplet energy differences is analyzed. Shell model calculations reproduce the new data but the necessary nuclear charge-dependent phenomenology is not fully explained by modern nucleon-nucleon potentials.
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30.
  • Gellanki, Jnaneswari, et al. (författare)
  • Extensive Gamma-ray Spectroscopy of Band Structures in 62Zn
  • 2012
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 86:3
  • Tidskriftsartikel (refereegranskat)abstract
    • An experimental study of the Zn-62 nucleus has been performed by combining the data sets from four fusion-evaporation reaction experiments. Apart from the previously published data, the present results include ten new rotational band structures and two more superdeformed bands. The Gammasphere Ge-detector array in conjunction with the 4 pi charged-particle detector array Microball allowed for the detection of gamma rays in coincidence with evaporated light particles. The deduced level scheme includes some 260 excited states, which are connected with more than 450 gamma-ray transitions. Spins and parities of the excited states have been determined via directional correlations of. rays emitted from oriented states. The experimental characteristics of the rotational bands are analyzed and compared with results from cranked Nilsson-Strutinsky calculations. The present analysis, combined with available experimental results in the A similar to 60 mass region, can be used to improve the current set of Nilsson parameters in the N = 3 and N = 4 oscillator shells.
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31.
  • Guo, S., et al. (författare)
  • Evidence for pseudospin-chiral quartet bands in the presence of octupole correlations
  • 2020
  • Ingår i: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 807
  • Tidskriftsartikel (refereegranskat)abstract
    • Three nearly degenerate pairs of doublet bands are identified in Ba-131. Two of them, with positive-parity, are interpreted as pseudospin-chiral quartet bands. This is the first time that a complete set of chiral doublet bands built on the pseudospin partners pi(d(5/2), g(7/2)) is observed. The chiral bands with opposite parity built on 3-quasiparticle configurations are directly connected by many E1 transitions, without involving an intermediary non-chiral configuration. The observed band structures in Ba-131 have been investigated by using the reflection-asymmetric particle rotor model. The energies and the electromagnetic transition ratios of the three pairs of doublet bands observed in Ba-131 are reproduced and they are interpreted as chiral doublet bands with three-quasiparticle configurations. It is the first time that multiple chiral bands are observed in the presence of enhanced octupole correlations and pseudospin symmetry. 
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32.
  • Karlgren, Daniel, et al. (författare)
  • High-angular-momentum structures in Zn-64
  • 2004
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69, s. 1-034330
  • Tidskriftsartikel (refereegranskat)abstract
    • High-angular-momentum states in Zn-64 were populated in the Ca-40(Si-28,4p) reaction at a beam energy of 122 MeV. Evaporated, light, charged particles were identified by the Microball, while gamma rays were detected using the Gammasphere array. The main focus of this paper is on two strongly coupled, collective bands. The yrast band, which was previously known, has been linked to lower-lying states establishing the excitation energies and angular momenta of in-band states for the first time. The newly identified excited band decays to the yrast band but firm angular-momentum assignments could not be made. In order to interpret these structures cranked-Nilsson-Strutinsky calculations have been performed. The calculations have been extended to account for the distribution of nucleons within a configuration. The yrast collective band is interpreted as based on the pi(f(7/2))(-1)(p(3/2)f(5/2))(2)(g(9/2))(1)nu(p(3/2)f(5/2))(4)(g(9/2))(2) configuration. There are several possible interpretations of the second band but it is difficult to distinguish between the different possibilities.
  •  
33.
  • Lv, B. F., et al. (författare)
  • Experimental evidence for transverse wobbling bands in Nd-136
  • 2022
  • Ingår i: Physical Review C. - : American Physical Society (APS). - 2469-9985 .- 2469-9993. ; 105:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The nature of two high-spin bands in Nd-136 built on the two-quasiparticle configuration pi h(11/2)(2), predicted by the triaxial projected shell model as good candidates of transverse wobbling bands, are investigated experimentally. The mixing ratio of one Lambda I = 1 transition connecting the one-phonon and the zero-phonon wobbling bands is established from a high-statistics JuroGam II gamma-ray spectroscopy experiment by using the combined angular correlation and linear polarization method. The resulting wobbling excitation energy and ratios of reduced electromagnetic transition probabilities are in good agreement with results of a new particle-rotor model which rigidly couples the total angular momentum of two quasiparticles to a triaxial core in an orthogonal geometry, confirming thus the transverse wobbling nature of the bands.
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34.
  •  
35.
  • Rudolph, D., et al. (författare)
  • Experimental and shell-model study of excited states in 55Fe29 and related notes on 55Cu26
  • 2021
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 104:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The fusion-evaporation reaction 32S+28Si at 125-MeV beam energy was used to populate excited states in 55Fe. Combining the Gammasphere spectrometer with ancillary devices including the Microball CsI(Tl) array and a shell of neutron detectors, a comprehensive level scheme could be derived. The experimental results are compared with theoretical results from shell-model calculations. Taking into account isospin-symmetry breaking terms is found to considerably improve the shell-model description for 55Fe. This motivated a predictive case study of near-yrast states in the mirror nucleus 55Cu.
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36.
  • Rudolph, D., et al. (författare)
  • Single-particle and collective excitations in the N=28 isotones 54Fe and 53Mn
  • 2020
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985. ; 102:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The fusion-evaporation reaction 32S + 28Si at 125 MeV beam energy was used to populate high-spin states in the semimagic N = 28 nuclei 53Mn and 54Fe. With a combination of the Gammasphere spectrometer and ancillary devices including the Microball CsI(Tl) array, extensive high-spin level schemes are derived. They exhibit rotational-like collective structures and competing single-particle excitations. The experimental results are compared with predictions from shell-model calculations, for which the inclusion of isopin-symmetry-breaking terms is found to improve the description. An interpretation of the high-spin states is put forward using cranked Nilsson-Strutinsky calculations, indicative of contributions from collective excitations beyond some 8-MeV excitation energy and highlighting the importance of the g9/2 intruder orbital in this energy range.
  •  
37.
  • Sohler, D, et al. (författare)
  • Maximally Aligned States in the Proton Drip Line Nucleus 106Sb
  • 2005
  • Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 753:3-4, s. 251-262
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Sb-106 have been investigated in the Fe-54(Ni-58, 1α 1p1n) reaction by in-beam γ-spectroscopic methods using the EUROBALL detector array equipped with charged particle and neutron detectors. On the basis of measured γγ-coincidence relations, angular distributions, and linear polarization ratios a significantly extended level scheme has been constructed up to spin and parity I-π = (19(-)) and E-x ∼ 6.5 MeV. The experimental results are interpreted within the framework of the gdsh shell model using a realistic effective nucleon-nucleon interaction. Candidates for states with fully aligned angular momenta in the π(d(5/2), g(7/2))(1) v (d(5/2), g(7/2))(5) valence space are identified at 4338 and 5203 keV, as well as in the π(d(5/2), g(7/2))(1) V(d(5/2), g(7/2))(4)h(11/2)(1) space at 6087, 6573 and 6783 keV.
  •  
38.
  • Valiente-Dobon, JJ, et al. (författare)
  • Evidence for nontermination of rotational bands in Kr-74
  • 2005
  • Ingår i: Physical Review Letters. - 1079-7114. ; 95:23
  • Tidskriftsartikel (refereegranskat)abstract
    • Three rotational bands in Kr-74 were studied up to (in one case one transition short of) the maximum spin I-max of their respective single-particle configurations. Their lifetimes have been determined using the Doppler-shift attenuation method. The deduced transition quadrupole moments reveal a modest decrease, but far from a complete loss of collectivity at the maximum spin I-max. This feature, together with the results of mean field calculations, indicates that the observed bands do not terminate at I=I-max.
  •  
39.
  • Wadsworth, R., et al. (författare)
  • Evidence for shape coexistence at medium spin in Rb-76
  • 2011
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 701:3, s. 306-312
  • Tidskriftsartikel (refereegranskat)abstract
    • Four previously known rotational bands in Rb-76 have been extended to moderate spins using the Gammasphere and Microball gamma ray and charged particle detector arrays and the Ca-40(Ca-40,3pn) reaction at a beam energy of 165 MeV. The properties of two of the negative-parity bands can only readily be interpreted in terms of the highly successful Cranked Nilsson-Strutinsky model calculations if they have the same configuration in terms of the number of g(9/2) particles, but they result from different nuclear shapes (one near-oblate and the other near-prolate). These data appear to constitute a unique example of shape coexisting structures at medium spins. (C) 2011 Elsevier B.V. All rights reserved.
  •  
40.
  • Andreoiu, A., et al. (författare)
  • Pricing power system stabilisers using game theory
  • 2005
  • Ingår i: IEE Proceedings: Generation, Transmission and Distribution. - 1350-2360 .- 1359-7051. ; 152:6, s. 780-786
  • Tidskriftsartikel (refereegranskat)abstract
    • A method to quantify the individual contribution of power system stabilisers (PSSs) to enhance system performance is proposed. Enhancement in system performance from PSS is measured through increased system transfer capability and the margin of stability thus achieved, and considering an N-1 contingency criterion. The method is based on cooperative game theory and makes use of the Shapley value concept, pinpointing the importance of a particular PSS to the system performance in all possible combinations in which it can operate. Based on this quantification of the contribution of a PSS, a feasible financial compensation mechanism to pay generators for the services rendered is proposed and illustrated using a sample system. It is argued that, within a deregulated environment, it would be appropriate that generators having an online and optimally tuned PSS be regarded as PSS-control ancillary service providers.
  •  
41.
  • Ekman, Jörgen, et al. (författare)
  • Unusual Isospin-Breaking and Isospin-mixing Effects in the A=35 Mirror Nuclei
  • 2004
  • Ingår i: Physical Review Letters. - 1079-7114. ; 92:13
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states have been studied in Ar-35 following the O-16(Mg-24,1alpha1n)Ar-35 fusion-evaporation reaction at 60 MeV using the Ge-detector array GASP. A comparison with the mirror nucleus Cl-35 shows two remarkable features: (i) A surprisingly large energy difference for the 13/2(-) states, in which the hitherto overlooked electromagnetic spin-orbit term is shown to play a major role, and (ii) a very different decay pattern for the 7/2(-) states, which provides direct evidence of isospin mixing.
  •  
42.
  • Fahlander, Claes, et al. (författare)
  • Evolution and Destruction of Shapes in 59Cu
  • 2002
  • Ingår i: Challenges of Nuclear Structure. Proceedings of the 7th International Spring Seminar on Nuclear Physics. - 9810247257 ; , s. 393-400
  • Konferensbidrag (refereegranskat)abstract
    • An extensive high-spin level scheme has been established in 59Cu using a heavy-ion fusion evaporation reaction and the GAMMASPHERE multidetector array in conjunction with MICROBALL. Next to the spherical states at low excitation energy a large number of regular sequences of high-energy γ-ray transitions have been observed, which form rotational bands with various degree of deformation. For the yrast superdeformed band about 90% of the intensity of the discrete γ decay-out, distributed over about 30 decay paths, is known, which allows for a detailed study of this decay-out process. Two of the deformed bands were found to decay by prompt proton emission into two different spherical states of 58Ni, in direct competition with the γ decay-out process
  •  
43.
  • Fahlander, Claes, et al. (författare)
  • Excited States in 103Sn: Neutron Single-particle Energies with Respect to 100Sn
  • 2001
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813 .- 1089-490X. ; 63:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Gamma-ray lines from Sn-103 have been identified for the first time using EUROBALL and ancillary detectors. The level scheme of Sn-103 has been established by means of particle-gated gamma gamma coincidences. The energy spacing between the g(7/2) and d(5/2) neutron single-particle orbitals is determined from the excited states in Sn-103.
  •  
44.
  • Gellanki, Jnaneswari, et al. (författare)
  • High-spin Structure Studies in 62Zn
  • 2012
  • Ingår i: Physica Scripta. - 0031-8949. ; T150
  • Tidskriftsartikel (refereegranskat)abstract
    • A detailed experimental study of the Zn-62 nucleus was conducted by combining the data sets from four fusion-evaporation reaction experiments. Apart from the previous published data, the present results include ten new rotational band structures and two new superdeformed bands. The GAMMASPHERE Ge-detector array in conjunction with the 4 pi charged-particle detector array Microball allowed for detection of gamma-rays in coincidence with evaporated light particles. The deduced level scheme includes some 260 excited states, which are connected with 450 gamma-ray transitions. The multipolarities have been assigned via directional correlations of gamma-rays emitted from oriented states. The experimental characteristics of the rotational bands are analyzed and compared with the results from the cranked Nilsson-Strutinsky calculations.
  •  
45.
  • Palacz, M., et al. (författare)
  • Investigations of Neutron Deficient Nuclei Close to 100Sn with EUROBALL
  • 2001
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254 .- 1509-5770. ; 32, s. 999-1003
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states of nuclei in the vicinity of Sn-100 have been studied using: the EUROBALL detector array. Gamma-ray lines from Sn-103 have been identified for the first time, and a level scheme of low-lying excited states of Sn-103 has been established. New constraints on energies of single particle orbitals with respect to the Sn-100 core are obtained.
  •  
46.
  • Rudolph, Dirk, et al. (författare)
  • Gamma-decay Lifetime Measurements in the Second Minimum of 58Cu
  • 2001
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 63:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The individual lifetimes of three low-lying states in the proton-decaying well-deformed rotational band in the second minimum of the N = Z nucleus Cu-58 were determined. Doppler-shift attenuated gamma -ray lineshapes were analyzed following the fusion-evaporation reaction C-40,(Mg-24,1 alpha 1p1n)Cu-58 and using the EUROBALL gamma -ray spectrometer coupled to ancillary detector systems. The deduced transitional quadrupole moments confirm the predicted increase of deformation towards the bottom of the band. The gamma decay-out strength hints towards a nonstatistical pattern.
  •  
47.
  • Rudolph, Dirk, et al. (författare)
  • Isospin and Deformation Studies in the Odd-odd N = Z Nucleus 54Co
  • 2010
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 82:5
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in the odd-odd N = Z nucleus Co-54 have been investigated by the fusion-evaporation reaction Si-28(S-32,1 alpha 1p1n)Co-54. Gamma-ray information gathered with the Ge detector array Gammasphere was correlated with evaporated particles detected in the charged particle detector system Microball and a 1 pi neutron detector array. A significantly extended excitation scheme of Co-54 is presented, which includes a candidate for the isospin T = 1, 6(+) state of the 1f(7/2)(-2) multiplet. The results are compared to large-scale shell-model calculations in the fp shell. Effective interactions with and without isospin-breaking terms have been used to probe isospin symmetry and isospin mixing. A quest for deformed high-spin rotational cascades proved negative. This feature is discussed by means of cranking calculations.
  •  
48.
  • Rudolph, Dirk, et al. (författare)
  • The Lifetime of the Proton-decaying 8915 keV State in 58Cu
  • 2001
  • Ingår i: Nuclear Physics, Section A. - 0375-9474. ; 694, s. 132-146
  • Tidskriftsartikel (refereegranskat)abstract
    • Energy correlations between gamma -ray transitions and the prompt proton decay line in Cu-58 were studied by means of the fusion-evaporation reaction Ca-40(Mg-24,1 alpha 1p1n) using the EUROBALL spectrometer coupled to ancillary detector devices. A lifetime of 0.06 < tau < 0.58 ps for the 8915 keV proton-decaying state in Cu-58 is deduced. (C) 2001 Elsevier Science B.V. All rights reserved.
  •  
49.
  • Sohler, D, et al. (författare)
  • Neutron Excitations Across the N=50 Shell Gap in 102In
  • 2002
  • Ingår i: Nuclear Physics, Section A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 708:3-4, s. 181-189
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of In-102 has been investigated by in-beam gamma-spectroscopic methods. Knowledge on the excited states of this nucleus has significantly been extended. Three cascades of transitions were observed to exceed the spin-energy domain spanned by the pig(9/2)(-1)v(d(5/2),g(7/2))(3) configurations. The new high spin states at similar to 4 MeV excitation energy could be assigned to the pig(9/2)(-1)v(d(5/2), g(7/2))(2)h (11/2) configuration, while at least those at 4.733, 5.192 and 5.853 MeV most likely arise from the vg(9/2) --> vd(5/2), g(7/2) one-particle-one-hole excitation across the N = 50 shell closure.
  •  
50.
  • Valiente-Dobon, JJ, et al. (författare)
  • High-spin rotational structures in Kr-76
  • 2005
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 71:3
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Kr-76(36)40 have been populated in the Ca-40(Ca-40,4p)Kr-76 fusion-evaporation reaction at abeam energy of 165 MeV and studied using the Gammasphere and Microball multidetector arrays. The ground-state band and two signature-split negative parity bands of Kr-76 have been extended to similar to 30 (h) over bar. Lifetime measurements. using the Doppler-shift attenuation method show that the transition quadrupole moment of these three bands decrease as they approach their maximum-spin states. Two signatures of a new rotational structure with remarkably rigid rotational behavior have been identified. The high-spin properties of these rotational bands are analyzed within the framework of configuration-dependent cranked Nilsson-Strutinsky calculations.
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