D<scp>IRECT</scp> R<scp>EACTIONS WITH</scp> E<scp>XOTIC</scp> N<scp>UCLEI</scp>

Hansen, P. G.; Tostevin, J. A.

doi:10.1146/annurev.nucl.53.041002.110406

Cited by 418 publications

(643 citation statements)

References 103 publications

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“…Single-nucleon knockout reactions, initiated by secondary beams of short-lived exotic nuclei at fragmentation beam energies, have significant cross sections and have been shown to be a powerful tool for studying the structure of light-and medium-mass nuclei [1,2]. In almost all cases the reaction populates a number of hole states in the reaction residue leading to sizable cross sections to several discrete, bound residue excited states.…”

Section: Introductionmentioning

confidence: 99%

Dynamical core deformation effects on single-nucleon knockout reactions at fragmentation beam energies

2005

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The effects of core deformation and of its dynamical reorientation and rotational excitation on the inclusive single-neutron knockout reaction cross sections on light spherical target nuclei are examined. The projectile nuclei are modeled within the framework of a weak-coupling, quadrupole-deformed core-plus-neutron two-body model. We formulate the inclusion of this non-spectator-core degree of freedom within the nonperturbative eikonal model and calculate the elastic and inelastic breakup (or stripping) neutron-removal cross sections. We apply the methods to model the single-neutron removal reactions induced by 11 Be and 17 C secondary fragmentation beams incident on a 9 Be target. Our calculations indicate that dynamical deformation effects on the elastic breakup component of the knockout cross section can be significant. This is the largest effect. The more geometrical stripping cross section is found to be hardly changed by the inclusion of the deformed core degree of freedom.

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Section: Introductionmentioning

confidence: 99%

Dynamical core deformation effects on single-nucleon knockout reactions at fragmentation beam energies

2005

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“…[6]. Shell-model calculations were carried out in the πsd − νpf basis with the SDPF-U Hamiltonian [7] using the code NUSHELLX [8].…”

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Rotational and neutron-hole states inS43via the neutron knockout and fragmentation reactions

et al. 2009

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The recent assertion that shape coexistence occurs in the neutron-rich isotope 43 S implies that a state observed at 940 keV in a previous study is a rotational excitation of the deformed ground state. Here we use results from two intermediate-energy reactions to demonstrate that this state-assigned an energy of 971 keV in the present work-is indeed a rotational state. This result strengthens the case for shape coexistence in 43 The neutron-rich nuclei in the vicinity of 44 S presently provide a critical testing ground for the idea that neutron shell structure is significantly different close to the neutron dripline than it is in the valley of stability. Gaudefroy et al. [1] recently published the results of a g-factor measurement of an isomer in 43 S at 320 keV and argued on the basis of their result that spherical and deformed shapes coexist in that nucleus.Gaudefroy et al. interpret the 320 keV isomer as a spherical f 7/2 single-neutron hole state (with J π = 7/2 − ), and assign the ground state J π = 3/2 − on the basis of the E2 transition deexciting the isomer. They further argue that the ground state must be deformed to have this J π value. Finally, they suggest that a state observed by Ibbotson et al. [2] and assigned an energy of 940 keV is a J π = 7/2 − rotational excitation of the ground state. In the present work, we report on a test of this interpretation of the state observed by Ibbotson et al. using both the direct single-neutron knockout reaction 9 Be( 44 S, 43 S)X and the reaction 9 Be( 45 Cl, 43 S)X. The latter involves both direct and nondirect removal of a neutron and proton, and is referred to here as a fragmentation reaction. The relatively small cross sections for population of this state observed in these reactions supports its interpretation as a rotational excitation built on the ground state and strengthens the case for shape coexistence in 43 S.The experiment was performed at the Coupled-Cyclotron Facility of the National Superconducting Cyclotron Laboratory at Michigan State University. A cocktail beam comprising 84% 44 S and 14% 45 Cl was produced by fragmentation of a 140 MeV/nucleon 48 Ca primary beam incident on a 705 mg/cm 2 9 Be fragmentation target. Components of the secondary beam were separated in the A1900 fragment separator [3] and delivered to a 376 mg/cm 2 thick 9 Be reaction target mounted at the target position of the S800 magnetic spectrograph [4]. In the one-neutron knockout measurement, 1.5 × 10 8 44 S beam particles were incident on the reaction target. The midtarget beam energy was 92 MeV/nucleon. The fragmentation measurement was performed with a total of 1.6 × 10 8 45 Cl beam particles and a midtarget beam energy of 98 MeV/nucleon. Incoming beam particles were identified from their time-of-flight difference measured between scintillators mounted at the extended focal plane of the A1900 and at the object of the S800 analysis line. Projectile-like reaction products were identified by the time of flight to the focal plane of the S800 and energy loss in the S800 i...

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“…2 using a novel experimental technique, one-and two-nucleon knockout from beams of exotic nuclei 6,7 . We present strong evidence for a well-developed proton subshell closure at Z=14, the near degeneracy of the s 1/2 and d 3/2 proton orbits in the vicinity of 42 Si, and a nearly spherical shape for 42 Si.…”

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confidence: 99%

“…A single strong γ-ray transition appears in this 43 P γ-ray spectrum at 184(3) keV, the first γ-ray observed in this nucleus. The single-nucleon knockout reaction preferentially populates states that have a structure of a single nucleon hole in the beam nucleus 6 . The measured cross sections for populating the two states of 43 P observed here -the ground state and the excited state deexcited by the 184 keV γ-rayare large, so an interpretation of these two states as d 3/2 and s 1/2 single-proton states is justified.…”

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confidence: 99%