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Finite, bound, many-body systems, where the interaction operator, V = ∑ v i j , is local and happens to strongly dominate the kinetic energy operator, T = ∑ t i , display a classical limit from diagonalizing V alone, hence a clear picture of interparticle correlations, such as steric blocking emerges. This limit exhibits intrinsic symmetries and also fluctuations from mass formulae. This work investigates how such emergent symmetries and fluctuations might be extrapolated to physical situations where T is reinstated. [ABSTRACT FROM AUTHOR]

The spectra of mass-11 nuclei are unusual, and so pose a challenge for nuclear-structure theory. Relating to nucleon emission, the set of isobars range from being well-bound ( 11 B, 11 C) through weakly bound ( 11 Li, 11 Be), to being proton unstable ( 11 N, 11 O). To add complexity, the weakly bound 11 Li takes the form of a two-nucleon halo nucleus. A self-consistent approach to understand this set of nuclei is especially important as the mirror pair 11 Be- 11 N exhibit a parity-inverted ground state compared to their neighboring nuclei. Herein, the Multi-Channel Algebraic Scattering method (MCAS) has been used to describe the low excitation spectra of those isobars in terms of nucleon-nucleus clusters. A collective model description of the low-excitation states of the mass-10 mass-10 core nuclei has been used to form the coupled-channel interactions required in the method. For comparison, and to understand the underlying configurations, a shell model approach has been used to obtain those spectra with no-core (0 + 2 + 4) ħ ω and (0 + 2) ħ ω shell-model spaces for the mass 10 and mass 11 nuclei respectively. The results of the calculations suggest the need of a strong coupling in the collective coupled-channel vibrational model. In particular, the strong coupling of the collective 2 1 + state of 10 Be to the valence neutron plays a decisive role in forming the positive parity ground state in 11 Be; an effect confirmed by the shell-model results. [ABSTRACT FROM AUTHOR]

Using a modified version of Jacques Raynal's program, DWBA98, we have analyzed cross-section data from a select set of charge exchange (p, n) reactions leading to isobaric analogue states of the target ground states. The Melbourne g-matrix model of the NN interaction has been used to specify both the relevant optical model potentials and the transition interactions. The formulation used defines transition amplitudes in terms of nucleon state occupancies in the ground states of the targets. Skyrme-Hartree-Fock and shell-model structures have been used for the input spectroscopic information. Targets of 92 Zr, 42 , 48 Ca, 208 Pb, and 6 He have been considered specifically. [ABSTRACT FROM AUTHOR]

The SCRIT and FAIR/ELISe experiments are the first to attempt to measure directly electron scattering form factors from nuclei far from stability. This will give direct information for the (one-body) charge densities of those systems, about which there is little information available. The SCRIT experiment will be taking data for medium-mass exotic nuclei, while the electron-ion collider at ELISe, when constructed, will be able to measure form factors for a wide range of exotic nuclei, as available from the radioactive ion beams produced by the FAIR experiment. Other facilities are now being proposed, which will also consider electron scattering from exotic nuclei at higher energies, to study short-range correlations in exclusive reactions. This review will consider all available information concerning the current status (largely theoretical) of electron scattering from exotic nuclei and, where possible, complement such information with equivalent information concerning the neutron densities of those exotic systems, as obtained from intermediate energy proton scattering. The issue of long- and short-range correlations will be discussed, and whether extending such studies to the exotic sector will elicit new information. [ABSTRACT FROM AUTHOR]

Constrained energy minimizations of a many-body Hamiltonian return energy landscapes e ( b ) where b ≡ 〈 B 〉 represents the average value(s) of one (or several) collective operator(s), B , in an “optimized” trial state Φ b , and e ≡ 〈 H 〉 is the average value of the Hamiltonian in this state Φ b . It is natural to consider the uncertainty, Δ e , given that Φ b usually belongs to a restricted set of trial states. However, we demonstrate that the uncertainty, Δ b , must also be considered, acknowledging corrections to theoretical models. We also find a link between fluctuations of collective coordinates and convexity properties of energy surfaces. [ABSTRACT FROM AUTHOR]

Predictions of cross sections and analyzing powers using g-folding optical potentials for the scattering of 71A MeV 6,8He ions from (polarized) hydrogen are compared with data. A g-folding model in which exchange amplitudes are evaluated explicitly was used with wave functions of 6,8He specified from a no-core shell model that used a complete (0 + 2 + 4)ħɷ basis. The analyzing powers reveal some sensitivities to the details of the wave functions, especially in the case of halo nuclei. [ABSTRACT FROM AUTHOR]

Abstract: A systematic strategy for the calculation of density functionals (DFs) consists in coding informations about the density and the energy into polynomials of the degrees of freedom of wave functions. DFs and Kohn–Sham potentials (KSPs) are then obtained by standard elimination procedures of such degrees of freedom between the polynomials. Numerical examples illustrate the formalism. [Copyright &y& Elsevier]

Abstract: Proton and neutron densities from Skyrme–Hartree–Fock (SHF) calculations are used to generate non-local (g-folding) proton–nucleus optical potentials. They are formed by folding the densities with realistic nucleon–nucleon interactions. The potentials are then used to calculate differential cross sections and spin observables for proton scattering. Good agreement with data has been found, supporting those found previously when using SHF charge densities in analyses of electron scattering data. That agreement was improved by use of (shell model) occupation numbers to constrain the HF iterations. That, in part, is also the case with analyses of proton scattering data. The g-folding method is extended to exotic nuclei by including data for neutron-rich sd-shell nuclei from the inverse kinematics of scattering from hydrogen. [Copyright &y& Elsevier]

Abstract: Differential cross section and analyzing power data from 197 MeV scattering and longitudinal and transverse form factors for electron scattering to low lying states in 10B have been analyzed as tests of the structure of the nuclear states when they are described using a no-core shell model. While the results obtained from the shell model clearly show the need of other elements, perhaps three-body forces, to explain the observed spectrum, the reasonable level of agreement obtained in the analyses of the scattering data suggest that the wave functions from our shell model with only a two-body potential are credible through the volume of the nucleus. Any changes to the wave functions with the introduction of additional terms in the shell model Hamiltonian, therefore should be relatively minor. [Copyright &y& Elsevier]

Abstract: Diverse means are used to investigate the spectra of the radioactive, exotic ions, 17,19C. First, estimates have been made using a shell model for the systems. Information from those shell model studies were then used in evaluating cross sections of the scattering of 17,19C ions from hydrogen. Complementing those studies, a multichannel algebraic scattering (MCAS) theory for n+16,18C coupled-channel problems has been used to identify structures of the compound systems. The results show that the shell model structure assumed for these ions is reasonable with little need of effective charges. The conditions that two excited states exist within a few hundred keV of the ground state places some restriction upon the structure models. Other positive parity states are expected in the low-lying spectra of the two nuclei. [Copyright &y& Elsevier]

Abstract: Differential cross sections from fully microscopic calculations of inelastic proton scattering off 208Pb are compared to experimental scattering data for incident proton energies between 65 and 201 MeV. The required nucleon–nucleus interactions were formed by folding nuclear structure information with a reliable nucleon–nucleon effective interaction that has no adjustable parameter. The absence of phenomenological normalisation in our approach offers the possibility to interpret with confidence the calculated results in terms of the quality of the underlying nuclear structure description: a feature that had been reserved, until recently, to the electron probe. We have used this method to investigate the effect of long range correlations embedded in excited states on calculated inelastic observables and demonstrate the sensitivity of nucleon scattering predictions to details of the nuclear structure. [Copyright &y& Elsevier]

Abstract: Various model applications in nuclear structure and reactions have been formulated starting with the Feshbach projection formalism. In recent studies a truncated excluded space has been enumerated to facilitate calculation and identify a convergence in expansions within that truncation. However, the effect of any remainder must be addressed before results from such can be considered physical. [Copyright &y& Elsevier]

Abstract: Shell model wave functions have been used to form microscopic g-folding optical potentials with which elastic scattering data from 8He, 10,11C, and 18,20,22O scattering on hydrogen have been analyzed. Those potentials, the effective two-nucleon interaction used in their formation, and the shell model details, then have been used in distorted wave approximation calculations of differential cross sections from inelastic scattering to the first excited states of five of those radioactive ions. [Copyright &y& Elsevier]

Abstract: The elastic electron scattering form factors, longitudinal and transverse, from the He and Li isotopes and from 8B have been studied. Large space shell model functions have been assumed. The precise distribution of the neutron excess has little effect on the form factors of the isotopes though there is a mass dependence in the charge densities. However, the form factors of the proton-rich nucleus, 8B, are significantly changed by the presence of the proton halo. [Copyright &y& Elsevier]

Abstract: Data from the inelastic scattering of electrons, and of intermediate energy protons and pions leading to “stretched” configuration states near 19 MeV excitation in 16O as well as from charge exchange scattering to an isobaric analogue () state in 16F have been analyzed to ascertain the degree of isospin mixing contained within those states and of the amount of – particle–hole excitation strength they exhaust. The electron and proton scattering data have been analyzed using microscopic models of the structure and reactions, with details constrained by analyses of elastic scattering data. [Copyright &y& Elsevier]

The spectra of mass-19 nuclei are unusual and pose a challenge for theoretical models of their structure. Herein the Multi-Channel Algebraic Scattering (MCAS) method has been used with a collective (vibrational model) description of the low-excitation states of 18 O and 18 Ne to describe the spectra of four mass-19 nuclei, specifically the mirror pairs ( 19 O, 19 Na) and ( 19 F, 19 Ne). This coupled-channel approach allows for the effects of the Pauli principle to be included using non-local orthogonalizing pseudo-potentials. By the coupling of neutrons to the core nuclei, we obtain states in 19 O (a neutron coupled to 18 O) and 19 Ne (a neutron coupled to 18 Ne). Mirror symmetry and addition of the Coulomb interaction gives states in 19 F (a proton coupled to 18 O) and 19 Na (a proton coupled to 18 Ne). However, the same compound nuclei may be described as the coupling of more complicated nuclear clusters. We obtain the states in 19 F as the coupling of an α to 15 N, as well as the coupling of 3 H to 16 O. Similarly, states in 19 Ne have been obtained from the coupling of an α to 15 O and of the coupling of 3 He to 16 O. Finally, as the method allows extraction of scattering matrices, it has been used to evaluate cross sections for the elastic scattering of low-energy neutrons from 18 O and of low-energy α particles from 15 O. [ABSTRACT FROM AUTHOR]

A multi-channel algebraic scattering (MCAS) approach has been used to analyze the spectra of two hypernuclear systems, $^9_\Lambda{\rm Be}$ and $^{13}_\Lambda\rm C$. The splitting of the two odd-parity excited levels ($\frac{1}{2}^-$ and $\frac{3}{2}^-$) at 11 MeV excitation in $^{13}_\Lambda\rm C$ is driven mainly by the weak Λ-nucleus spin–orbit force, but the splittings of the $\frac{3}{2}^+$ and $\frac{5}{2}^+$ levels in both $^{9}_\Lambda{\rm Be}$ and $^{13}_\Lambda\rm C$ have a different origin. These cases appear to be dominated by coupling to the collective 2+ states of the core nuclei. Using simple phenomenological potentials as input to the MCAS method, the observed splitting and level ordering in $^{9}_\Lambda{\rm Be}$ is reproduced with the addition of a weak spin–spin interaction acting between the hyperon and the spin of the excited target. With no such spin–spin interaction, the level ordering in $^{9}_\Lambda{\rm Be}$ is inverted with respect to that currently observed. In both hypernuclei, our calculations suggest that there are additional low-lying resonant states in the Λ-nucleus continua. [ABSTRACT FROM AUTHOR]

Abstract: Differential cross sections and analyzing powers for elastic proton scattering from, and for inelastic proton scattering to a set of states in, 12C, 20Ne, 24Mg, 28Si and 40Ca, and for a set of energies between 35 to 250 MeV, have been analyzed. A g-folding model has been used to determine optical potentials and a microscopic distorted wave approximation taken to analyze the inelastic data. The effective nucleon–nucleon interactions used to specify the optical potentials have also been used as the transition operators in the inelastic scattering processes. Shell and large space Hartree–Fock models of structure have been used to describe the nuclear states. The calculations are in general agreement with the data when the cross sections are in excess of (elastic) and (inelastic, ), which suggests that other small effects (such as coupled-channel diagrams) are necessary before agreement between theory and data can be found at large scattering angles. However, the agreement found otherwise gives credibility to the models of structure considered. [Copyright &y& Elsevier]

Two causes of nonlocality inherent in nucleon-nucleus scattering are considered. They are the results of two-nucleon antisymmetry of the projectile with each nucleon in the nucleus and the dynamic polarization potential representation of channel coupling. For energies ∼ 40 -300MeV, a g -folding model of the optical potential is used to show the influence of the knock-out process that is a result of the two-nucleon antisymmetry. To explore the dynamic polarization potential caused by channel coupling, a multichannel algebraic scattering model has been used for low-energy scattering. [ABSTRACT FROM AUTHOR]

Sturmian theory for nucleon-nucleus scattering is discussed in the presence of all the phenomenological ingredients necessary for the description of weakly-bound (or particle-unstable) light nuclear systems. Currently, we use a macroscopic potential model of collective nature. The analysis shows that the couplings to low-energy collective-core excitations are fundamental but they are physically meaningful only if the constraints introduced by the Pauli principle are taken into account. The formalism leads one to discuss a new concept, Pauli hindrance, which appears to be important to understand the structure of weakly-bound and unbound systems. [Copyright &y& Elsevier]

Abstract: Cross-section and analyzing power data from scattering to the states at 11.58 and 14.35 MeV in 28Si, taken with 80, 100, 134, and 180 MeV protons, have been analyzed using a distorted wave approximation with microscopically defined wave functions. The results of our analyses of those data, taken in conjunction with the analysis of an M6 electron scattering form factor, suggest that in the specification of the two states, and respectively of the strengths of isoscalar and isovector excitations from the ground state as described by a Skyrme–Hartree–Fock model. The energy variation of data also suggests that the non-central components of the effective interactions at 80 and 100 MeV may need to be enhanced. [Copyright &y& Elsevier]

A multi-channel algebraic scattering (MCAS) method has been used to solve coupled sets of Lippmann-Schwinger equations for the $ \alpha + {}^{6}{\rm He}$ cluster system, so finding a model spectrum for Be to more than 10MeV excitation. Three states of He were included and the resonance character of the two excited states taken into account in finding solutions. A model Hamiltonian has been found that gives very good agreement with the known bound states and with some low-lying resonances of Be . More resonance states are predicted than those which have been observed as yet. The method also yields S -matrices which we have used to evaluate low-energy He - $ \alpha$ scattering cross sections. Reasonable reproduction of low-energy differential cross sections and of energy variation of cross sections measured at fixed scattering angles have been found. Enlarging the channel space by including two higher energy states of He , assuming values for their spin-parities, leads to an enlarged spectrum for Be in which the number and distribution of resonances show similarity to the known spectrum. [ABSTRACT FROM AUTHOR]

One theoretical method for studying nuclear scattering and resonances is via the multichannel algebraic scattering (MCAS) formalism. Studies to date with this method have used a simple collective-rotor prescription to model target states with which a nucleon couples. While generally these target states all belong to the same rotational band, for certain systems it is necessary to include coupling to states outside of that main band. Here, we extend MCAS to allow couphng of different strengths between such states and the rotor band. This is an essential consideration in studying the example examined herein, the scattering of neutrons from 22Ne. [ABSTRACT FROM AUTHOR]

The article studies the scattering of neutrons from Ne22 with the multichannel algebraic scattering (MCAS) formalism. It also utilizes the extended form of MCAS to allow nucleon coupling of different strengths between some of the set of target states and the rotor band. It also discusses the use of simple collective-rotor prescription to model target states associated with nucleon coupling.

The article focuses on a research that involves coupling of the two target-state bands in the study of n+22Ne system at low energy states. Topics discussed include the development of the algebraic variational (MCAS) rotor potentials for NA scattering, the scattering of neutrons from 22Ne, and the solutions of coupled-channel Lippmann-Schwinger equations involved in the MCAS method.

The article focuses on a study to examine scattering of neutrons from Neon (Ne) 22Ne with the multichannel algebraic scattering (MCAS) formalism. It also utilizes extended form of MCAS to allow nucleon coupling of different strengths between some of the set of target states and rotor band. It also mentions the use of simple collective-rotor prescription to model target states associated with nucleon coupling.

The article presents a study analyzing nuclear scattering and resonances via the multichannel algebraic scattering (MCAS) formalism. Topics discussed include effect of multichannel algebraic scattering formalism on a nucleon-nucleus system, experimentally observed resonance features of MCAS cross section, and qualitative analysis of MCAS elastic cross section for neutron scattering.

The article presents a study focusing on coupling to two target-state bands in the study of the n + 22Ne system at low energy. The findings include use of multichannel algebraic scattering (MCAS) to allow coupling of different strengths between model target states and rotor band, the MCAS method showing solutions of coupled-channel Lippmann-Schwinger equations in momentum space with nucleon-nucleus interactions, and effects of additional channels on spectrum and cross section.

Abstract: By performing studies of the structure of the spectra of mass-17 nuclei we discuss specific aspects of the Multi-Channel Algebraic Scattering (MCAS) method. We devote particular attention to the comparison with results from large-scale shell-model calculations, the treatment of Pauli-forbidden or -hindered states, and to the collective/coupled nature of the states obtained in our model. By using different shell-model spaces as platform to assess the MCAS method, we question statements raised recently about the validity of this method on the basis of a small-scale shell-model approach. [Copyright &y& Elsevier]

Abstract: The structure of 17C is used to define a nuclear interaction that, when used in a multichannel algebraic scattering theory for the system, gives a credible definition of the (compound) excitation spectra. When couplings to the low-lying collective excitations of the 16C-core are taken into account, both sub-threshold and resonant states about the threshold are found. Adding Coulomb potentials to that nuclear interaction, the method is used for the mirror system of to specify the low excitation spectrum of the particle unstable 17Na. We compare the results with those of a microscopic cluster model. A spectrum of low excitation resonant states in 17Na is found with some differences to that given by the microscopic cluster model. The calculated resonance half-widths (for proton emission) range from ∼2 to . [Copyright &y& Elsevier]

The vector analyzing power has been measured for the elastic scattering of neutron-rich 6He from polarized protons at 71 MeV/nucleon making use of a newly constructed solid polarized proton target operated in a low magnetic field and at high temperature. Two approaches based on local one-body potentials were applied to investigate the spin-orbit interaction between a proton and a 6He nucleus. An optical model analysis revealed that the spin-orbit potential for 6He is characterized by a shallow and long-ranged shape compared with the global systematics of stable nuclei. A semimicroscopic analysis with an α+n+n cluster folding model suggests that the interaction between a proton and the α core is essentially important in describing the p+6He elastic scattering. The data are also compared with fully microscopic analyses using nonlocal optical potentials based on nucleon-nucleon g matrices. [ABSTRACT FROM AUTHOR]

The question of how the scattering cross section changes when the spectra of the colliding nuclei have low-excitation particle-emitting resonances is explored using a multichannel algebraic scattering method. As a test case, the particle-unstable nucleus 8Be has been considered as a target. Nucleon-nucleus scattering cross sections, as well as the spectra of the compound nuclei formed, have been determined from calculations that consider, as well as those that disregard, particle-emission widths of the target nuclear states. The resonant character of the unstable excited states introduces a problem because the low-energy tails of these resonances can intrude into the subthreshold, bound-state region. This unphysical behavior needs to be corrected by modifying, in an energy-dependent way, the shape of the target resonances from the usual Lorentzian form. The resonance function must smoothly reach zero at the elastic threshold. We explore herein a way of achieving this condition. [ABSTRACT FROM AUTHOR]

The structure of 6He is explored with proton elastic and inelastic scattering to the first 2+ excited state (Q=−1.8 MeV) of 6He in the inverse kinematics using a 24.5 A MeV 6He beam. The distorted wave approximation (DWA) with an optical potential obtained by folding an effective nucleon–nucleon (NN) g-matrix with the 6He density matrix elements as given by a large basis shell model is used to analyse the data. The comparison of predictions with the data confirms the view that 6He has an extended (halo) neutron matter distribution. [Copyright &y& Elsevier]

In a previous Letter [Phys. Rev. Lett. 96, 072502 (2006)], the multichannel algebraic scattering (MCAS) technique was used to calculate spectral properties for proton-unstable 15F and its mirror, 15C. This achieved a close match to the then-new data for p+14O elastic scattering and predicted several unusually narrow resonances at higher energies. Subsequently, such narrow resonance states were discovered. New cross section data has been published characterizing the shape of the Jπ=1/2- resonance. Herein we update that first MCAS analysis and its predictions. We also study the spectra of the set of mass-15 isobars 15C, 15N, 15O, and 15F, using the MCAS method seeking a consistent Hamiltonian for clusterization with a neutron and a proton, separately, coupled to core nuclei 14C and 14O. [ABSTRACT FROM AUTHOR]

We employ a collective vibration coupled-channel model to describe the nucleon-16O cluster systems, obtaining low-excitation spectra for 17O and 17F. Bound and resonance states of the compound systems have been deduced, showing good agreement with experimental spectra. Low-energy scattering cross sections of neutrons and protons from 16O also have been calculated and the results compare well with available experimental data. [ABSTRACT FROM AUTHOR]

What effect do particle-emitting resonances have on the scattering cross section? What physical considerations are necessary when modeling these resonances? These questions are important when theoretically describing scattering experiments with radioactive ion beams which investigate the frontiers of the table of nuclides, far from stability. Herein, a novel method is developed that describes resonant nuclear scattering from which centroids and widths in the compound nucleus are obtained when one of the interacting bodies has particle unstable resonances. The method gives cross sections without unphysical behavior that is found if simple Lorentzian forms are used to describe resonant target states. The resultant cross sections differ significantly from those obtained when the states in the coupled channel calculations are taken to have zero width, and compound-system resonances are better matched to observed values. [ABSTRACT FROM AUTHOR]