The Darmstadt-Heidelberg-crystal-ball

Metag, V.; Habs, D.; Helmer, Karl G.; Helmolt, U.v.; Heyng, H.W.; Kolb, B.; Pelte, D.; Schwalm, D.; Hennerici, W.; Hennrich, Heiko; Himmele, G.; Jaeschke, E.; Repnow, R.; Wahl, W.; Simon, R. S.; Albrecht, R.

doi:10.1007/3-540-12001-7_251

Cited by 26 publications

(93 citation statements)

References 4 publications

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“…A stable beam of 40 Ar was accelerated by the linear accelerator UNILAC and by the synchrotron SIS-18 at the GSI facility to an energy of 490A MeV and impinged on a 4-g/cm 2 -thick 9 Be target to induce fragmentation reactions, in which the 27 Ne and 26 Ne nuclei were produced. They were subsequently selected by the fragment separator (FRS) [25], whose magnetic rigidity was set to 9.05 Tm in order to favor the transmission of nuclei with A/Z ∼ 2.7.…”

Section: Methodsmentioning

confidence: 99%

“…These secondary nuclei were transmitted to the R 3 B/LAND experimental setup [26], where they were identified on an event-by-event basis using (i) their energy loss in the position-sensitive silicon PIN diode (PSP) detector and (ii) their time of flight measured between two plastic scintillators, one located at the end of the FRS beam line, and the other (start detector POS) placed a few meters before a 922 mg/cm 2 CH 2 reaction target. A total of 2.5 × 10 5 (3.8 × 10 5 ) nuclei of 27 Ne ( 26 Ne) impinged on the CH 2 target, with an energy at the entrance of 432 (456)A MeV.…”

Section: Methodsmentioning

confidence: 99%

“…This secondary target was surrounded by the 159 NaI crystals of the 4π Crystal Ball detector [27], each having a length of 20 cm and covering a solid angle of 77 msr. It allowed the detection of photons from excited fragments decaying in flight and recoil protons at angles larger than ±7°in the laboratory frame.…”

Section: Methodsmentioning

confidence: 99%

“…In addition, the photomultipliers of the 64 most forward crystals had a second lower-gain readout, for the detection of recoil protons originating from knockout reactions. Two pairs of double-sided silicon strip detectors (DSSSD), with active areas of 72 × 41 mm 2 and strips 300 μm thick (110 μm pitch), were placed before and after the reaction target to determine the energy loss and to track the incoming and outgoing nuclei, e.g., 27 Ne and 26 F, respectively, in the case of a one-proton knockout reaction from 27 Ne populating bound states in 26 atomic number Z of the transmitted nuclei was obtained from the determination of their energy losses in the DSSSD, placed after the target, and in the TFW. The mass (A) identification is obtained from the combined position information of the fragments in the DSSSD placed after the target, in the two GFIs and in the TFW, and from their velocity β, which was deduced from their time of flight between the POS detector and the TFW [28,29].…”

Section: Methodsmentioning

confidence: 99%

“…The knockout of a 0d 5/2 proton from 27 Ne should leave the 26 F nucleus in the (π 0d 5/2 ) 1 (ν0d 3/2 ) 1 configuration and favor the 1 The structure of the ground state of 26 F was also investigated by the one-neutron-knockout reaction at relativistic energies [20]. The narrow inclusive momentum distribution of the 25 F residue pointed to the presence of valence neutrons in the 1s 1/2 state, in apparent contradiction with the neutron 0d 3/2 configuration of the 1 + ground state proposed above.…”

Section: Introductionmentioning

confidence: 99%

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Effective proton-neutron interaction near the drip line from unbound states in F25,26

Vandebrouck¹,

Lepailleur²,

Sorlin³

et al. 2017

Phys. Rev. C

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Background: Odd-odd nuclei, around doubly closed shells, have been extensively used to study proton-neutron interactions. However, the evolution of these interactions as a function of the binding energy, ultimately when nuclei become unbound, is poorly known. The 26 F nucleus, composed of a deeply bound π 0d 5/2 proton and an unbound ν0d 3/2 neutron on top of an 24 O core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a J π = 1 1 + − 4 1 + multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The J π = 1 1 + , 2 1 + , 4 1 + bound states have been determined, and only a clear identification of the J π = 3 1 + is missing. Purpose: We wish to complete the study of the J π = 1 1 + − 4 1 + multiplet in 26 F, by studying the energy and width of the J π = 3 1 + unbound state. The method was first validated by the study of unbound states in 25 F, for which resonances were already observed in a previous experiment. Method: Radioactive beams of 26 Ne and 27 Ne, produced at about 440A MeV by the fragment separator at the GSI facility were used to populate unbound states in 25 F and 26 F via one-proton knockout reactions on a CH 2 target, located at the object focal point of the R 3 B/LAND setup. The detection of emitted γ rays and neutrons, added to the reconstruction of the momentum vector of the A − 1 nuclei, allowed the determination of the energy of three unbound states in 25 F and two in 26 F. Results: Based on its width and decay properties, the first unbound state in 25 F, at the relative energy of 49(9) keV, is proposed to be a J π = 1/2 − arising from a p 1/2 proton-hole state. In 26 F, the first resonance at 323(33) keV is proposed to be the J π = 3 1 + member of the J π = 1 1 + − 4 1 + multiplet. Energies of observed states in 25,26 F have been compared to calculations using the independent-particle shell model, a phenomenological shell model, and the ab initio valence-space in-medium similarity renormalization group method. Conclusions: The deduced effective proton-neutron interaction is weakened by about 30-40% in comparison to the models, pointing to the need for implementing the role of the continuum in theoretical descriptions or to a wrong determination of the atomic mass of 26 F.

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