Two-neutron knockout from neutron-deficient<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">Ar</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>34</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">S</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>30</mml:mn></mml:mrow></mml:mmultiscripts></mml:mat

Eur. Phys. J. Spec. Top.

2007

Self Cite

Abstract. Final-state-exclusive two-nucleon removal reaction data from fast fragmentation beams can provide a demanding test of the microscopic two-nucleon transition densities calculated from large-basis shell model wave functions. The sensitivity of measured partial cross sections to pairing and other correlations is discussed. It is also suggested that the widths of the momentum distributions of these partial cross sections will exhibit a strong dependence on the final-state of the residue and the projectile structure.PACS. 25.60.-t Reactions induced by unstable nuclei -23.40.Hc Relation with nuclear matrix elements and nuclear structure

Section: Introductionsupporting

confidence: 53%

“…These were studied using intermediate-energy beams of neutron-deficient 34 Ar, 30 S, and 26 Si [8]. These are shown in Figure 4 in terms of the measured and calculated (0 + ) ground state branching ratios.…”

mentioning

confidence: 99%

Reaction spectroscopy at fragmentation beam energies – recent advances in studies of two-nucleon removal

Eur. Phys. J. Spec. Top.

2007

Self Cite

“…[1][2][3]. More recently, reaction studies have exploited the direct nature of the reaction mechanism for the removal of two well-bound (like) nucleons from already asymmetric nuclei to populate and probe the structure of the most neutron-rich and neutron-deficient nuclei [4][5][6][7]. These analyses exploit the accuracy and simplicity of the eikonal model for the reaction dynamics at the intermediate energies, of order 100 MeV/nucleon, of fragmentation facilities [5,7].…”

Section: Introductionmentioning

confidence: 99%

One- and two-neutron removal from the neutron-rich carbon isotopes

Simpson

2009

Phys. Rev. C

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Reactions that involve the fast removal (knockout) of one and two neutrons from the neutron-rich carbon isotopes, 15−19 C, by light nuclear targets are studied within an eikonal reaction model. Shell model calculations are used to describe the excitation energy spectra and the structures of the carbon isotopes. The calculated one-neutron knockout cross sections from the A C isotopes, to particle-bound configurations of the A−1 C residues, are in agreement with the available experimental data. The two-neutron removal cross sections, producing A−2 C residues, receive contributions from both the direct, single-step two-neutron knockout and the indirect mechanism, involving single-neutron removal strength to neutron-unbound excited states in the A−1 C system followed by neutron emission. The latter two-step reaction mechanism is shown to be dominant. The empirical odd-even staggering of the single-neutron separation energies along the carbon isotopic chain is reflected in the two-neutron removal data. This staggering and the magnitudes of the two-neutron removal cross sections are reproduced qualitatively by the theoretical calculations.

“…Very similar suppression factors are required to describe the three measured two-neutron removal reaction cases also. These are discussed more fully elsewhere [10,7].…”

Section: Effects On Two-nucleon Removal Calculationsmentioning

confidence: 99%

“…Four such reactions on sd-shell nuclei have been measured recently [6,7]. The availability of data on sd-shell nuclei, for which the predictive power of the shell-model is very high, thus allows a first assessment of the sensitivity of the reaction mechanism to the assumed two-nucleon structures in a rather clean, direct-reaction regime.…”

Section: Introductionmentioning

confidence: 99%

Probing the shell model using nucleon knockout reactions

2006

J. Phys.: Conf. Ser.

Abstract. We assess the sensitivity of the intermediate energy, direct two-nucleon knockout reaction mechanism to details of the correlated motions of the two removed nucleons -as might be revealed by measurements of partial cross sections to different final states of the mass A−2 reaction residues. Comparisons of new reaction calculations with recent data for exotic nuclei in the sd-shell suggest that this sensitivity is significant and that the coherence of the twonucleon configurations to the reaction allows small wave function components to be probed. The relative yields for the different J π transitions are well described by the USD shell model calculations, however the measured cross sections require an overall suppression of the shell model two-nucleon spectroscopic strengths. IntroductionOne-nucleon knockout reactions from intermediate-energy (projectile fragmentation) beams are an increasingly important tool for mapping the single-particle structures of nuclei with exotic neutron-and proton-number combinations. The single-nucleon removal cross sections are large (several tens of mb) and both the efficiency and selectivity of the associated reaction measurements are high. This allows an examination of orbitals of both the weakly-bound (excess) and strongly-bound (deficient) nucleon species at their respective (and very displaced) Fermi surfaces [1,2]. Exclusive (with respect to the knockout residue final states) single-nucleon knockout reaction analyses on light nuclear targets (usually 9 Be and 12 C), with energies from 40 MeV -1 GeV/nucleon, are now able to assess structure model predictions of level orderings and shell-gaps and of details of level occupations and spectroscopic strengths in some of the most rare, unstable species. Examples are discussed in [1,3,4] and in references therein.In contrast, two-nucleon removal reactions -and what they can teach us -are less well understood. The intrinsic two-nucleon removal cross sections are now smaller (of order 1 mb) and their theoretical interpretation is also more complicated. Different [j 1 ⊗ j 2 ] configurations of the two-nucleons now contribute coherently to the cross section [5] resulting in a less transparent connection between data and the underlying structures. An added complication is that the reactions will, in general, proceed by both (i) a sudden two-nucleon knockout component with direct population of the mass A−2 residue, and (ii) indirect, two-step mechanisms -involving one-nucleon knockout to excited, intermediate fragments of mass A−1, followed by nucleon