Threshold Effects in Neutron Elastic Scattering

Wells, J.T.; Tucker, Allen B.; Meyerhof, W. E.

doi:10.1103/physrev.131.1644

Cited by 13 publications

(4 citation statements)

References 22 publications

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“…state a + n j . Of particular interest is a non-analytic behavior of direct reaction cross-section near the particle emission threshold [175][176][177][178][179]. It manifests itself by a discontinuity in the cross-section and/or of its derivatives (the so-called Wigner cusp); it often arises from a redistribution of particle flux when a new reaction channel opens.…”

Section: Overlap Integrals and Spectroscopic Factors In The Gsmmentioning

confidence: 99%

Shell model in the complex energy plane

Michel

Nazarewicz

Płoszajczak

et al. 2008

J. Phys. G: Nucl. Part. Phys.

259

378

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Section: Overlap Integrals and Spectroscopic Factors In The Gsmmentioning

confidence: 99%

Shell model in the complex energy plane

Michel

Nazarewicz

Płoszajczak

et al. 2008

J. Phys. G: Nucl. Part. Phys.

259

378

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“…This coupling effect has been studied theoretically [40,41,42,43,45,36,10] and experimentally [46,47,48,49] in connection with the Wigner threshold anomaly. The channelchannel continuum coupling influences both the anomalous and regular crosssection components.…”

Section: Definitionsmentioning

confidence: 99%

“…The modification of the cross section in one channel manifests itself due to the unitarity of the scattering matrix in other open channels. This coupling effect has been studied theoretically [40,41,42,43,45,36,10] and experimentally [46,47,48,49] in connection with the Wigner threshold anomaly. The channelchannel continuum coupling influences both the anomalous and regular crosssection components.…”

Section: Definitionsmentioning

confidence: 99%

Continuum coupling and single-nucleon overlap integrals

2007

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The presence of a particle continuum, both of a resonant and non-resonant character, can significantly impact spectroscopic properties of weakly bound nuclei and excited nuclear states close to, and above, the particle emission threshold. In the framework of the continuum shell model in the complex momentum-plane, the so-called Gamow Shell Model, we discuss salient effects of the continuum coupling on the one-neutron overlap integrals and the associated spectroscopic factors in neutron-rich helium and oxygen nuclei. In particular, we demonstrate a characteristic near-threshold energy dependence of the spectroscopic factors for different ℓ-waves. We show also that the realistic radial overlap functions, which are needed for the description of transfer reactions, can be generated by single-particle wave functions of the appropriately chosen complex potential.

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“…As the shape of the cusp strongly depends on orbital angular momentum (is strongest in s and p waves), it was early realized that the presence of cusp anomaly could provide structural information about reaction products [3,4,9].The Wigner-cusp phenomenon has been studied experimentally and theoretically in various areas of physics: pion-nucleus scattering [9, 10], electron-molecule scattering [11], electron-atom scattering [12], and ultracold atom-diatom scattering [13]. In low-energy nuclear physics, threshold effects have been investigated in, e.g., charge-exchange reactions [14], neutron elastic scattering [15], and deuteron stripping [16]. Abramovich et al [17] reviewed threshold phenomena in nuclear reactions, including those with the light neutron-rich systems such as 6 He, 10 Be, and 10 Li (see also Ref.…”

mentioning

confidence: 99%

Threshold effects in multichannel coupling and spectroscopic factors in exotic nuclei

2007

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In the threshold region, the cross section and the associated overlap integral obey the Wigner threshold law that results in the Wigner-cusp phenomenon. Due to flux conservation, a cusp anomaly in one channel manifests itself in other open channels, even if their respective thresholds appear at a different energy. The shape of a threshold cusp depends on the orbital angular momentum of a scattered particle; hence, studies of Wigner anomalies in weakly bound nuclei with several lowlying thresholds can provide valuable spectroscopic information. In this work, we investigate the threshold behavior of spectroscopic factors in neutron-rich drip-line nuclei using the Gamow Shell Model, which takes into account many-body correlations and the continuum effects. The presence of threshold anomalies is demonstrated and the implications for spectroscopic factors are discussed.In 1948, based on general principles, Wigner predicted [1] a characteristic behavior (a cusp) of scattering and reaction cross sections in the vicinity of a reaction threshold. This particular behavior (often referred to as the Wigner's threshold law or the Wigner-cusp phenomenon) was given a quantitative explanation a decade later [2,3,4,5,6,7]. In particular, it has been noted [3,4,5,6,8] that, due to the unitarity of the scattering matrix and the resulting flux conservation, the presence of a threshold anomaly in an opening reaction channel can trigger an appearance of Wigner cusps in other open channels with lower thresholds. As the shape of the cusp strongly depends on orbital angular momentum (is strongest in s and p waves), it was early realized that the presence of cusp anomaly could provide structural information about reaction products [3,4,9].The Wigner-cusp phenomenon has been studied experimentally and theoretically in various areas of physics: pion-nucleus scattering [9, 10], electron-molecule scattering [11], electron-atom scattering [12], and ultracold atom-diatom scattering [13]. In low-energy nuclear physics, threshold effects have been investigated in, e.g., charge-exchange reactions [14], neutron elastic scattering [15], and deuteron stripping [16]. Abramovich et al. [17] reviewed threshold phenomena in nuclear reactions, including those with the light neutron-rich systems such as 6 He, 10 Be, and 10 Li (see also Ref. [18]) that are of particular interest in the context of this work. The influence of threshold effects on the cross section and the strength function, hence the spectroscopic factor (SF) of a threshold state was pointed out in Refs. [8,19].The purpose of this study is many-fold. Firstly, we investigate whether the Wigner-cusp phenomenon appears naturally in a microscopic many-body approach rooted in an effective inter-nucleon interaction. The second goal is to investigate the influence of threshold effects and the coupling to the non-resonant continuum on overlap integrals, or spectroscopic factors. We demonstrate that the energy dependence of SFs caused by an opening of a reaction channel can be described at the shell-m...

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Threshold Effects in Neutron Elastic Scattering

Cited by 13 publications

References 22 publications

Shell model in the complex energy plane

Shell model in the complex energy plane

Continuum coupling and single-nucleon overlap integrals

Threshold effects in multichannel coupling and spectroscopic factors in exotic nuclei

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