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Abstract: The setup and experimental techniques for measurements of zero-degree inelastic scattering and reactions involving light ions with the K=600 magnetic spectrometer at iThemba LABS are described. Measurements were performed for inelastic proton scattering at an incident energy of 200MeV for targets ranging from 27Al to 208Pb. An energy-resolution of 45keV (FWHM) was achieved by utilizing the faint-beam dispersion-matching technique. A background subtraction procedure was applied and allowed for the extraction of excitation energy spectra with low background. Measurements of the (p,t) reaction at zero degrees for E p =100 and 200MeV benefited from the difference in magnetic rigidity between the reaction products and the beam particles, resulting in background-free spectra with an excitation energy-resolution of 32 and 48keV (FWHM), respectively, and a scattering angle resolution of 0.55° (FWHM). The addition of Double Sided Silicon Strip Detectors (DSSSD) at backward scattering angles allowed for coincident measurements of particle-decay of states excited in the (p,t) reaction at . [Copyright &y& Elsevier]

The 16O(α,α′) reaction was studied at θlab=0° at an incident energy of Elab=200 MeV using the K600 magnetic spectrometer at iThemba LABS. Proton decay and α decay from the natural parity states were observed in a large-acceptance silicon strip detector array at backward angles. The coincident charged-particle measurements were used to characterize the decay channels of the 06+ state in 16O located at Ex=15.097(5) MeV. This state is identified by several theoretical cluster calculations to be a good candidate for the 4-α cluster state. The results of this work suggest the presence of a previously unidentified resonance at Ex≈15 MeV that does not exhibit a 0+ character. This unresolved resonance may have contaminated previous observations of the 06+ state. [ABSTRACT FROM AUTHOR]

The reaction 58Ni(p,³He)56Co to several discrete, low-lying states in 56Co was investigated. Angular distributions of the analyzing power as well as differential cross sections are presented at incident energies of 80, 100, and 118 MeV. Macroscopic zero-range distorted-wave Born approximation calculations are in fairly good agreement with the experimental data in this incident energy range. This has important implications for studies of inclusive reactions in which light composite particles are emitted. [ABSTRACT FROM AUTHOR]

The existence of the giant pairing vibration (GPV) in 120Sn and 208Pb was investigated using the (p,t) reaction at incident proton energies of 50 MeV and 60 MeV for the scattering angles 0° and 7°. No clear signature for the GPV was found, providing an upper limit for the cross section of smax?=?0.2 mb. Theoretical interpretations for the low cross section of the GPV are discussed. [ABSTRACT FROM AUTHOR]

Experiments investigating the fine structure of the Isovector Giant Dipole Resonances (IVGDR) have been carried out on target nuclei 40,42,44,48Ca with 200 MeV proton inelastic scattering reactions using the high-energy resolution capability and the zero-degree set-up at the K600 magnetic spectrometer of the iThemba LABS, Cape Town, South Africa. Quasi-free scattering background contributions in the experimental data have been removed by applying a novel method of Discrete Wavelet Transform (DWT) analysis. Energy scales extracted are compared with the state-of-the-art theoretical calculations within the framework of the Quasiparticle- RPA and Relativistic Quasiparticle Time Blocking Approximation (RQTBA). For 40,48Ca, these calculations consider all major processes (Landau damping, escape width, spreading width) contributing to the damping of the IVGDR. [ABSTRACT FROM AUTHOR]

The phenomenon of fine structure of the Isoscalar Giant Quadrupole Resonance (ISGQR) has been studied with high energy-resolution proton inelastic scattering at iThemba LABS in the chain of stable even-mass Nd isotopes covering the transition from spherical to deformed ground states. A wavelet analysis of the background-subtracted spectra in the deformed 146, 148, 150 Nd isotopes reveals characteristic scales in correspondence with scales obtained from a Skyrme RPA calculation using the SVmas10 parameterization. A semblance analysis shows that these scales arise from the energy shift between the main fragments of the K = 0 , 1 and K = 2 components. [ABSTRACT FROM AUTHOR]

Proton inelastic scattering experiments at energy E p = 200 MeV and a spectrometer scattering angle of 0° were performed on 144,146,148,150 Nd and 152 Sm exciting the IsoVector Giant Dipole Resonance (IVGDR). Comparison with results from photo-absorption experiments reveals a shift of resonance maxima towards higher energies for vibrational and transitional nuclei. The extracted photo-absorption cross sections in the most deformed nuclei, 150 Nd and 152 Sm, exhibit a pronounced asymmetry rather than a distinct double-hump structure expected as a signature of K -splitting. This behaviour may be related to the proximity of these nuclei to the critical point of the phase shape transition from vibrators to rotors with a soft quadrupole deformation potential. Self-consistent random-phase approximation (RPA) calculations using the SLy6 Skyrme force provide a relevant description of the IVGDR shapes deduced from the present data. [ABSTRACT FROM AUTHOR]

The fine structure of the IsoVector Giant Dipole Resonance (IVGDR) in the doubly-magic nuclei 40,48Ca observed in inelastic proton scattering experiments under 0 ∘ is used to investigate the role of different mechanisms contributing to the IVGDR decay width. Characteristic energy scales are extracted from the fine structure by means of wavelet analysis. The experimental scales are compared to different theoretical approaches allowing for the inclusion of complex configurations beyond the mean-field level. Calculations are performed in the framework of RPA and beyond-RPA in a relativistic approach based on an effective meson-exchange interaction, with the UCOM effective interaction and, for the first time, with realistic two- plus three-nucleon interactions from chiral effective field theory employing the in-medium similarity renormalization group. All models highlight the role of Landau fragmentation for the damping of the IVGDR, while the differences in the coupling strength between one particle-one hole (1p-1h) and two particle-two hole (2p-2h) correlated (relativistic) and non-correlated (non-relativistic) configurations lead to very different pictures of the importance of the spreading width resulting in wavelet scales being a sensitive measure of their interplay. The relativistic approach with particle-vibration coupling, in particular, shows impressive agreement with the number and absolute values of the scales extracted from the experimental data. [ABSTRACT FROM AUTHOR]

Differential cross sections of isoscalar and isovector spin-M1 (P+ → 1+) transitions are measured using high-energy-resolution proton inelastic scattering at Ep = 295 MeV on 24Mg, 28Si, 32S, and 36Ar at 0°-l 4°. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to Ex = 16 MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transitions, while the matrix elements for isovector spin-M1 transitions are quenched by an amount comparable with the analogous Gamow-Teller transitions on those target nuclei. [ABSTRACT FROM AUTHOR]

The electric dipole strength distribution in 120 Sn has been extracted from proton inelastic scattering experiments at E p = 295 MeV and at forward angles including 0°. It differs from the results of a Sn 120 ( γ , γ ′ ) experiment and peaks at an excitation energy of 8.3 MeV. The total strength corresponds to 2.3(2)% of the energy-weighted sum rule and is more than three times larger than what is observed with the ( γ , γ ′ ) reaction. This implies a strong fragmentation of the E1 strength and/or small ground state branching ratios of the excited 1 − states. [ABSTRACT FROM AUTHOR]

The excited states of the 20Ne nucleus from the ground state to Ex = 25 MeV were investigated with the 22Ne(p,t)20Ne reaction at a beam energy of Ep = 60 MeV using the QDD magnetic spectrometer at iThemba LABS. Narrow, low-spin Jπ = 0+, l-, and 2+ states have been observed for the first time at high-excitation energies in 20Ne, namely at Ex = 17.67, 18.84, 20.59, 21.16, 21.80, and 22.5 MeV. Shell-model and coupled reaction channel calculations were performed to determine the nature of the newly observed states. Candidates for T - 2 states are proposed at 3.86(5), 4.43(5) MeV and 5.07(5) MeV above the lowest 0+, T = 2 state at Ex = 16.73 MeV. Two of these T = 2 candidates appear to result from core excitations in the Op shell. The state at Ex = 22.5 MeV, which could not be interpreted by the shell-model calculations, is a tentative candidate for the 5-α cluster state. [ABSTRACT FROM AUTHOR]

Knowledge of the low-lying monopole strength in C 12 —the Hoyle state in particular—is crucial for our understanding of both the astrophysically important 3 α reaction and of α -particle clustering. Multiple theoretical models have predicted a breathing mode of the Hoyle State at E x ≈ 9 MeV, corresponding to a radial in-phase oscillation of the underlying α clusters. The C 12 (α , α ′) C 12 and C 14 (p , t) C 12 reactions were employed to populate states in 12C in order to search for this predicted breathing mode. A self-consistent, simultaneous analysis of the inclusive spectra with R -matrix lineshapes, together with angular distributions of charged-particle decay, yielded clear evidence for excess monopole strength at E x ≈ 9 MeV which is highly collective. Reproduction of the experimentally observed inclusive yields using a fit, with consistent population ratios for the various broad states, required an additional source of monopole strength. The interpretation of this additional monopole resonance as the breathing-mode excitation of the Hoyle state would provide evidence supporting a D 3 h symmetry for the Hoyle state itself. The excess monopole strength may complicate analysis of the properties of the Hoyle state, modifying the temperature dependence of the 3 α rate at T 9 ≳ 2 and ultimately, the predicted nucleosynthesis in explosive stars. [ABSTRACT FROM AUTHOR]

High-energy-resolution 56Fe(3He, t)56Co reaction measurements were performed at forward angles including 0°. From the spectra obtained, the splitting of the Fermi transition strength and thus the isospin mixing between the Jπ = 0+ isobaric analog state (IAS) at 3.60 MeV and a neighboring 0+ state at 3.53 MeV have been investigated. In order to distinguish between states excited in Fermi and Gamow-Teller (GT) transitions, the measurements were performed at two 3He beam energies of 140 and 100 MeV/nucleon. Owing to the different incident energy dependencies of the στ- and τ-type effective interaction strengths, it is expected that the Fermi transitions are stronger relative to GT transitions at lower beam energies. Therefore the excitation of a state by the Fermi transition could be identified by the ΔL = 0 angular distribution and the ratio of transition strengths at these two incident energies. In the energy region around the IAS at 3.60 MeV, it was found that the state at 3.53 MeV is also excited by the Fermi transition and thus it has Jπ values of 0+. A value of 32.3(5) keV could be deduced for the off-diagonal matrix element of the Hamiltonian that causes the isospin mixing. A corresponding isospin impurity of 28 ± 1% was obtained. [ABSTRACT FROM AUTHOR]

The 12C excitation energy spectra populated in both proton and α-particle inelastic scattering measurements are examined. The data indicate the existence of a 2+ state at Ex = 9.75(0.15) MeV with a width of 750(150) keV. It is believed that this state corresponds to the 2+ excitation of the 7.65 MeV, 0+, Hoyle state, which acts as the main path by which carbon is synthesized in stars. A simultaneous Ä-matrix analysis of the two sets of data indicates that the 2+ state possesses a very large α-reduced width, approaching the Wigner limit. This would indicate that the state is associated with a highly clustered structure. The potential geometric arrangements of the clusters is discussed. [ABSTRACT FROM AUTHOR]

Scattering of protons of several hundred MeV is a promising new spectroscopic tool for the study of electric dipole strength in nuclei. A case study of 208Pb shows that, at very forward angles, Jπ = 1- states are strongly populated via Coulomb excitation. A separation from nuclear excitation of other modes is achieved by a multipole decomposition analysis of the experimental cross sections based on theoretical angular distributions calculated within the quasiparticle-phonon model. The B(El) transition strength distribution is extracted for excitation energies up to 9 MeV; that is, in the region of the so-called pygmy dipole resonance (PDR). The Coulomb-nuclear interference shows sensitivity to the underlying structure of the £ 1 transitions, which allows for the first time an experimental extraction of the electromagnetic transition strength and the energy centroid of the PDR. [ABSTRACT FROM AUTHOR]

The level density of 2+ states in 40Ca has been extracted in the energy region of the isoscalar giant quadrupole resonance from a fluctuation analysis of high-energy-resolution (p, p') data taken at incident energies of 200 MeV at the K600 magnetic spectrometer of iThemba LABS, South Africa. Quasifree-scattering cross sections were calculated to estimate their role as a background contribution to the spectra and found to be small. The shape of the background was determined from the discrete wavelet transform of the spectra using a biorthogonal wavelet function normalized at the lowest particle separation threshold. The experimental results are compared to widely used phenomenological and microscopic models. [ABSTRACT FROM AUTHOR]

A benchmark experiment on 208Pb shows that polarized proton inelastic scattering at very forward angles including 00 is a powerful tool for high-resolution studies of electric dipole (El) and spin magnetic dipole (MI) modes in nuclei over a broad excitation energy range to test up-to-date nuclear models. The extracted El polarizability leads to a neutron skin thickness rSkin = 0. 156+0.025-0.021 fm in 208Pb derived within a mean-field model [Phys. Rev. C 81, 051303 (2010)], thereby constraining the symmetry energy and its density dependence relevant to the description of neutron stars. [ABSTRACT FROM AUTHOR]

Abstract: The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in 40Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at . Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon–nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for 40Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle–two-hole (2p–2h) states. [Copyright &y& Elsevier]

The cluster structure of 12C is explored and recent measurements of proton inelastic scattering, suggesting a 2+ state close to 9.6 MeV are presented. Resonant scattering studies of 10Be + 4He used to populate resonances in 14C are briefly discussed. [ABSTRACT FROM AUTHOR]

Abstract: Large-angle quasielastic scattering has been studied in a high- nuclear reaction of the type leading to superheavy-element production by cold fusion. We show that despite the presence of strongly dissipative channels, and the complete absence of fusion, the notion of an external barrier distribution, determined by strong coupling to collective excitations of target and projectile, is still valid. Furthermore, our method allows us to deduce some properties of the deep-inelastic processes in this system. [Copyright &y& Elsevier]

High-resolution inelastic electron scattering experiments at the S-DALINAC and proton scattering experiments at iThemba LABS permit a thorough test of the nature of proposed one- and two-phonon symmetric and mixed-symmetric 2+ states of the nucleus 94Mo. The combined analysis reveals the one-phonon content of the mixed-symmetry state and its isovector character suggested by microscopic calculations. The purity of two-phonon 2+ states is extracted. [Copyright &y& Elsevier]

In intermediate-mass systems, collective excitations of the target and projectile can greatly enhance the subbarrier capture cross section σ cap by giving rise to a distribution of Coulomb barriers. For such systems, capture essentially leads directly to fusion [formation of a compound nucleus (CN)], which then decays through the emission of light particles (neutrons, protons, and alpha particles). Thus, the evaporation-residue (ER) cross section is essentially equal to σ cap. For heavier systems, the experimental situation is significantly more complicated owing to the presence of quasifission (QF) (rapid separation into two fragments before the CN is formed) and by fusion-fission (FF) of the CN itself. Thus, three cross sections need to be measured in order to evaluate σ cap. Although the ER essentially recoil along the beam direction, QF and FF fragments are scattered to all angles and require the measurement of angular distributions in order to obtain the excitation function and barrier distribution for capture. Two other approaches to this problem exist. If QF is not important, one can still measure just the ER cross section and try to reconstruct the corresponding σ cap through use of an evaporation-model code that takes account of the FF degree of freedom. Some earlier results on σ cap obtained in this way will be reanalyzed with detailed coupled-channels calculations, and the “extra-push” phenomenon discussed. One may also try to obtain σ cap by exploiting unitarity, that is, by measuring instead the flux of particles corresponding to quasielastic (QE) scattering from the Coulomb barrier. Some new QE results obtained for the 86Kr + 208Pb system at iThemba LABS in South Africa will be presented. [ABSTRACT FROM AUTHOR]

Abstract: Spectra of inclusive double differential cross sections of 3He and 6He fragments produced in the interaction of 12C with 93Nb at 400 MeV are measured and analyzed. As was found for the production of intermediate mass fragments in this and similar reactions involving light projectiles, the spectra can to a large extent be satisfactorily reproduced only by considering the contribution of projectile break-up as well as nucleon coalescence. [Copyright &y& Elsevier]

Abstract: A cryogenic horizontal single loop target has been designed, built, tested and operated for the experiment in Hall C at Jefferson Lab. The target cell is 20cm long, the loop volume is 6.5l and the target operates with the cryogenic pump fully immersed in the fluid. The target has been designed to operate at 30Hz rotational pump speed with either liquid hydrogen or liquid deuterium. The high-power heat exchanger is able to remove 1000W of heat from the liquid hydrogen, while the nominal electron beam with current of and energy of 3GeV deposits about 320W of heat into the liquid. The increase in the systematic uncertainty due to the liquid hydrogen target is negligible on the scale of a parity violation experiment. The global normalized yield reduction for beam is about 1.5% and the target density fluctuations contribute less than 238ppm (parts per million) to the total asymmetry width, typically about 1200ppm, in a bin. [Copyright &y& Elsevier]

High-energy-resolution magnetic spectrometer measurements have been used to determine the width of the 9.641 MeV 12C, 3- excited state. The width is found to be 48(2) keV with an R-matrix analysis. This would correspond to 30% of the Wigner limit, indicating a significant a-particle content to the state. This is a marked improvement on results of earlier studies that yielded 34(5) keV. [ABSTRACT FROM AUTHOR]

An experiment using the 11(³He,rf)12C reaction was performed at iThemba LABS at an incident energy of 44 MeV and analyzed with a high energy-resolution magnetic spectrometer, to reinvestigate states in 12C published in 1971. The original investigation reported the existence of an 11.16 MeV state in 12C that displays a 2+ nature. In the present experiment, data were acquired at laboratory angles of 25°, 30°, and 35°, which is part of the center-of-mass (cm.) angle range in the original measurements where a clear signature of such a state was observed. These new low-background measurements revealed no evidence of the previously reported state at 11.16 MeV in 12C. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes methods used in the manufacturing of chemically reactive targets such as calcium (natCa), lithium-6 (6Li) and molybdenum–97 (97Mo) for nuclear physics experiments at the iThemba LABS cyclotron facility (Faure, South Africa). Due to the chemical properties of these materials a suitable and controlled environment was established in order to minimize oxygen contamination of targets. Calcium was prepared by means of vacuum evaporation while lithium was cold rolled to a desired thickness. In the case of molybdenum, the metallic powder was melted under vacuum using an e-gun followed by cold rolling of the metal bead to a desired thickness. In addition, latest developments toward the establishment of a dedicated nuclear physics target laboratory are discussed. [Copyright &y& Elsevier]

Recent high-precision mass measurements and shell-model calculations [M. Brodeur et al., Phys. Rev. Lett. 108, 212501 (2012)] have challenged a longstanding explanation for the requirement of a cubic isobaric multiplet mass equation for the lowest A=9 isospin quartet. The conclusions relied upon the choice of the excitation energy for the second T=3/2 state in 9B, which had two conflicting measurements prior to this work. We remeasured the energy of the state using the 9Be(³He,t) reaction and significantly disagree with the most recent measurement. Our result supports the contention that continuum coupling in the most proton-rich member of the quartet is not the predominant reason for the large cubic term required for A=9 nuclei. [ABSTRACT FROM AUTHOR]

Background: The 22Ne(α,n)25Mg reaction is an important source of neutrons for the s-process. Direct measurement of this reaction and the competing 22Ne(α,γ)26Mg reaction are challenging due to the gaseous nature of both reactants, the low cross section and the experimental challenges of detecting neutrons and high-energy γ rays. Detailed knowledge of the resonance properties enables the rates to be constrained for s-process models. Purpose: Previous experimental studies have demonstrated a lack of agreement in both the number and excitation energy of levels in 26Mg. To try to resolve the disagreement between different experiments, proton and deuteron inelastic scattering from 26Mg have been used to identify excited states. Method: Proton and deuteron beams from the tandem accelerator at the Maier-Leibnitz Laboratorium at Garching, Munich, were incident upon enriched 26MgO targets. Scattered particles were momentum-analyzed in the Q3D magnetic spectrograph and detected at the focal plane. Results: Reassignments of states around Ex=10.8-10.83 MeV in 26Mg suggested in previous works have been confirmed. In addition, new states in 26Mg have been observed, two below and two above the neutron threshold. Up to six additional states above the neutron threshold may have been observed compared to experimental studies of neutron reactions on 25Mg, but some or all of these states may be due to 24Mg contamination in the target. Finally, inconsistencies between measured resonance strengths and some previously accepted Jπ assignments of excited 26Mg states have been noted. Conclusion: There are still a large number of nuclear properties in 26Mg that have yet to be determined and levels that are, at present, not included in calculations of the reaction rates. In addition, some inconsistencies between existing nuclear data exist that must be resolved in order for the reaction rates to be properly calculated. [ABSTRACT FROM AUTHOR]

Background: The 22Ne(α,n)25Mg reaction is one of the neutron sources for the s process in massive stars. The properties of levels in 26Mg above the α-particle threshold control the strengths of the 22Ne(α,n)25Mg and 22Ne(α,γ)26Mg reactions. The strengths of these reactions as functions of temperature are one of the major uncertainties in the s process. Purpose: Information on the existence, spin, and parity of levels in 26Mg can assist in constraining the strengths of the 22Ne(α,γ)26Mg and 22Ne(α,n)25Mg reactions, and therefore in constraining s-process abundances. Methods: Inelastically scattered α particles from a 26Mg target were momentum-analyzed in the K600 magnetic spectrometer at iThemba LABS, South Africa. The differential cross sections of states were deduced from the focal-plane trajectory of the scattered α particles. Based on the differential cross sections, spin and parity assignments to states are made. Results: A newly assigned 0+ state was observed in addition to a number of other states, some of which can be associated with states observed in other experiments. Some of the deduced Jπ values of the states observed in the present study show discrepancies with those assigned in a similar experiment performed at RCNP Osaka. The reassignments and additions of the various states can strongly affect the reaction rate at low temperatures. Conclusion: The number, location, and assignment of levels in 26Mg that may contribute to the 22Ne+α reactions are not clear. Future experimental investigations of 26Mg must have an extremely good energy resolution to separate the contributions from different levels. Coincidence experiments of 26Mg provide a possible route for future investigations. [ABSTRACT FROM AUTHOR]

The gamma strength function and level density of 1- states in 96Mo have been extracted from a high-resolution study of the (p, p′) reaction at 295 MeV and extreme forward angles. By comparison with compound nucleus γ decay experiments, this allows a test of the generalized Brink-Axel hypothesis in the energy region of the pygmy dipole resonance. The Brink-Axel hypothesis is commonly assumed in astrophysical reaction network calculations and states that the gamma strength function in nuclei is independent of the structure of the initial and final state. The present results validate the Brink-Axel hypothesis for 96Mo and provide independent confirmation of the methods used to separate gamma strength function and level density in γ decay experiments. [ABSTRACT FROM AUTHOR]

The 34 Ar (α, p) 37K reaction is believed to be one of the last in a sequence of (α, p) and (p, γ) reactions within the T z = - 1, s d -shell nuclei, known as the αp -process. This process is expected to influence the shape and rise times of luminosity curves coming from type I x-ray bursts (XRBs). With very little experimental information known on many of the reactions within the αp-process, stellar rates are calculated using a statistical model, such as Hauser-Feshbach. Questions on the applicability of a Hauser-Feshbach model for the 34Ar (α, p) 37K reaction arise due to level density considerations in the compound nucleus, 38Ca. We have performed high energy-resolution forward-angle 40Ca (p, t) 38Ca measurements with the K = 600 spectrograph at iThemba LABS in order to identify levels above the α-threshold in 38Ca. States identified in this work were then used to determine the 34Ar (α, p) 37K reaction rate based on a narrow-resonance formalism. Comparisons are made to two standard Hauser-Feshbach model predicted rates at XRB temperatures. [ABSTRACT FROM AUTHOR]

Background: Aspects of the nuclear structure of light α-conjugate nuclei have long been associated with nuclear clustering based on α particles and heavier α-conjugate systems such as 12C and 16O. Such structures are associated with strong deformation corresponding to superdeformed or even hyperdeformed bands. Superdeformed bands have been identified in 40Ca and neighboring nuclei and find good description within shell model, mean-field, and α-cluster models. The utility of the α-cluster description may be probed further by extending such studies to more challenging cases comprising lighter α-conjugate nuclei such as 24Mg, 28Si, and 32S. Purpose: The purpose of this study is to look for the number and energy of isoscalar 0+ states in 28Si. These states are the potential bandheads for superdeformed bands in 28Si corresponding to the exotic structures of 28Si. Of particular interest is locating the 0+ bandhead of the previously identified superdeformed band in 28Si. Methods: α-particle inelastic scattering from a natSi target at very forward angles including 0° has been performed at the iThemba Laboratory for Accelerator-Based Sciences in South Africa. Scattered particles corresponding to the excitation energy region of 6 to 14 MeV were momentum-analysed in the K600 magnetic spectrometer and detected at the focal plane using two multiwire drift chambers and two plastic scintillators. Results: Several 0+ states have been identified above 9 MeV in 28Si. A newly identified 9.71 MeV 0+ state is a strong candidate for the bandhead of the previously discussed superdeformed band. The multichannel dynamical symmetry of the semimicroscopic algebraic model predicts the spectrum of the excited 0+ states. The theoretical prediction is in good agreement with the experimental finding, supporting the assignment of the 9.71-MeV state as the bandhead of a superdeformed band. Conclusion: Excited isoscalar 0+ states in 28Si have been identified. The number of states observed in the present experiment shows good agreement with the prediction of the multichannel dynamical symmetry. [ABSTRACT FROM AUTHOR]

The isoscalar giant quadrupole resonance in 28Si and 27Al has been investigated with high-energy-resolution proton inelastic scattering at Ep=200MeV and at scattering angles close to the maximum of ΔL=2 angular distributions with the K600 magnetic spectrometer of iThemba LABS, South Africa. Characteristic scales are extracted from the observed fine structure with a wavelet analysis and compared for 28Si with random-phase approximation and second random phase approximation calculations with an interaction derived from the Argonne V18 potential by a unitary transformation. A recent extension of the method to deformed nuclei provides the best description of the data, suggesting the significance of Landau damping. [ABSTRACT FROM AUTHOR]

Abstract: The structure of the nucleus is discussed, in particular the spectrum of states above the α-decay threshold. A search for the 2+ excitation of the Hoyle-state is reported. The structural link between halo-like states and molecular states is explored in the case of . [Copyright &y& Elsevier]