| 1. |
- Meech, K. J., et al.
(författare)
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EPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign
- 2011
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Ingår i: Astrophysical Journal Letters. - London : IOP. - 2041-8213 .- 2041-8205. ; 734:L1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4?hr. Starting in 2010 August the period changed from 16.6?hr to near 19?hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO 2 -driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production.
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| 2. |
- Niedermaier, O., et al.
(författare)
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"Safe" Coulomb excitation of Mg-30
- 2005
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 94:17, s. 172501 (artno)-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient γ spectrometer MINIBALL. Using Mg-30 ions accelerated to an energy of 2.25 MeV/u together with a thin Ni-nat target, Coulomb excitation of the first excited 2(+) states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation γ-ray yields the B(E2;0(gs)(+)→ 2(1)(+)) value of Mg-30 was determined to be 241(31)e(2) fm(4). Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope Mg-30 resides outside the "island of inversion."
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| 3. |
- Niedermaier, O., et al.
(författare)
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The neutron-rich Mg isotopes: first results from MINIBALL at REX-ISOLDE
- 2005
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 752, s. 273-273
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient γ spectrometer MINIBALL. Using Mg-30 ions accelerated to an energy of 2.25 MeV/u together with a thin Ni-nat target, Coulomb excitation of the first excited 2(+) states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation γ-ray yields the B(E2;0(gs)(+)→ 2(1)(+)) value of Mg-30 was determined to be 241(31)e(2) fm(4). Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope Mg-30 resides outside the "island of inversion."
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| 4. |
- Scheit, H., et al.
(författare)
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Coulomb excitation of neutron-rich beams at REX-ISOLDE
- 2005
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 25:Suppl. 1, s. 397-402
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Konferensbidrag (refereegranskat)abstract
- After the successful commissioning of the radioactive beam experiment at ISOLDE (REX-ISOLDE) - an accelerator for exotic nuclei produced by ISOLDE - in 2002 and the promotion to a CERN user facility in 2003, first physics experiments using these beams were performed. Initial experiments focused on the region of deformation in the vicinity of the neutron-rich Na and Mg isotopes. Preliminary results on the neutron-rich Na and Mg isotopes show the high potential and physics opportunities offered by the exotic isotope accelerator REX in conjunction with the modern Germanium gamma spectrometer MINIBALL.
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| 5. |
- Stefanova, E. A., et al.
(författare)
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Four-quasiparticle alignments in Ge-66
- 2003
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Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 34:4, s. 2237-2240
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Tidskriftsartikel (refereegranskat)abstract
- Above angular momentum 10(+), we found two positive-parity sequences, connected by energetically staggered DeltaI = 1 M1 transitions. The total Routhian surface calculations predict a strong triaxial deformation for them. To our knowledge, this is the first observation of staggered M1 transitions in a deformed four-quasiparticle pi(g(9/2)(2))v(g(9/2)(2)) regime.
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| 6. |
- Stefanova, E. A., et al.
(författare)
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Four-quasiparticle alignments in Ge-66
- 2003
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 67:5
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Tidskriftsartikel (refereegranskat)abstract
- The neutron-deficient nucleus Ge-66 was populated at high spin in two experiments using the reaction Ca-40(S-32,alpha2p) at beam energies of 105 and 95 MeV. In the first experiment, a self-supporting Ca-40 target was used, while a gold-backed target of similar thickness was used in the second experiment. gamma rays were detected with the EUROBALL array, combined with the charged-particle detector array EUCLIDES and the Neutron Wall. The level scheme of Ge-66 was extended up to Eapproximate to18 MeV and I-pi=(23(-)). Above angular momentum 10(+), we found two sequences, connected by energetically staggered DeltaI=1 M1 transitions. The total Routhian surface calculations describe Ge-66 at lower spins as a gamma-soft nucleus having a moderate deformation of beta(2)approximate to0.23, while a triaxial deformation is predicted for the band structures above I-pi=10(+). To our knowledge, this is the first observation of staggered M1 transitions in a deformed four-quasiparticle pi(g(9/2)(2))nu(g(9/2)(2)) structure.
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| 7. |
- Stefanova, E. A., et al.
(författare)
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Observation of negative-parity high-spin states of As-68
- 2005
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 24:1, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- The neutron-deficient nucleus As-68 was populated at high spin in two experiments using the reaction Ca-40(S-32, 3pn) at beam energies of 105 and 95 MeV. A self-supporting and a gold-backed, highly enriched Ca-40 target were used. Gamma rays were detected with the EUROBALL array, combined with the charged-particle detector array EUCLIDES and the Neutron Wall. The As-68 level scheme was considerably extended, especially at negative parity and many previous spin-parity assignments were confirmed or rejected. The total-Routhian-surface (TRS) calculations find shape coexistence and γ softness for the negative- and positive-parity states, respectively.
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| 8. |
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| 9. |
- Stefanescu, I, et al.
(författare)
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High-spin states and band terminations in As-69
- 2004
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 70:4
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Tidskriftsartikel (refereegranskat)abstract
- Excited levels in As-69 were studied using the Ca-40(S-32,3p)As-69 reaction at 95 and 105 MeV beam energy. Gamma rays were detected with the EUROBALL spectrometer operated in conjunction with the Neutron Wall and the charged-particle detector array EUCLIDES. New level sequences with positive and negative parity were identified from 3p-gammagamma and gammagammagamma coincidences. Spins were assigned to many of the levels on the basis of directional correlations of oriented states measurements. The previously observed positive-parity band was extended to spin 45/2(+) and it was found to exhibit a crossing with another configuration identified up to spin 53/2(+). Three negative-parity bands were observed for the first time up to spins (43/2(-)), 39/2(-), and (41/2(-)). The previously known band was extended to spin (49/2(-)). No evidence for superdeformation was found, despite very high counting statistics. Configurations were assigned to each of the observed bands through comparisons to the cranked Nilsson-Strutinsky calculations.
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