Search

We studied the proton-rich T_{z}=-1 nucleus ^{70}Kr through inelastic scattering at intermediate energies in order to extract the reduced transition probability, B(E2;0^{+}→2^{+}). Comparison with the other members of the A=70 isospin triplet, ^{70}Br and ^{70}Se, studied in the same experiment, shows a 3σ deviation from the expected linearity of the electromagnetic matrix elements as a function of T_{z}. At present, no established nuclear structure theory can describe this observed deviation quantitatively. This is the first violation of isospin symmetry at this level observed in the transition matrix elements. A heuristic approach may explain the anomaly by a shape change between the mirror nuclei ^{70}Kr and ^{70}Se contrary to the model predictions.

12 pags., 11 figs., 2 tabs., The N= Z= 36 nucleus Kr has been studied by inelastic scattering at intermediate energies. Two targets, Be and Au, were used to extract the nuclear deformation length, δ, and the reduced E2 transition probability, B(E2). The previously unknown non-yrast 2 and 4 states as well as a new candidate for the octupole 3 state have been observed in the scattering on the Be target and placed in the level scheme based on γ- γ coincidences. The second 2 state was also observed in the scattering on the Au target and the B(E2;22+→01+) value could be determined for the first time. Analyzing the results in terms of a two-band mixing model shows clear evidence for a oblate-prolate shape coexistence and can be explained by a shape change from an oblate ground state to prolate deformed yrast band from the first 2 state. This interpretation is corroborated by beyond mean field calculations using the Gogny D1S interaction., We would like to thank the RIKEN accelerator and BigRIPS teams for providing the high intensity beams. We thank T. Furumoto for providing us with the optical potentials and A. Moro for giving access to an unpublished version of the FRESCO code. This work has been supported by UK STFC under Grant numbers ST/L005727/1 and ST/P003885/1, the Spanish Ministerio de Economía y Competitividad under Grants FPA2011-24553, FPA2014-52823-C2- 1-P, and PGC2018-094583-B-I00, the Program Severo Ochoa (SEV2014-0398), the European Research Council through the ERC Grant No. MINOS-258567, NKFIH (NN128072), and by the ÚNKP-19-4- DE-65 New National Excellence Program of the Ministry of Human Capacities of Hungary. G. K. acknowledges support from the János Bolyai research fellowship of the Hungarian Academy of Sciences. K. W. acknowledges the support from the Spanish Ministerio de Economía y Competitividad RYC-2017-22007.

We present a microscopic description of neutron and proton elastic and inelastic scattering off $^{206,207,208}\mathrm{Pb}$ and $^{209}\mathrm{Bi}$ together with new medium-energy (7.5--15.5 MeV) neutron elastic and inelastic scattering measurements for various low-energy levels. The Jeukenne, Lejeune, Mahaux (JLM) semimicroscopic folding model provides the relevant optical and transition potentials used to calculate the elastic and inelastic cross sections. Rearrangement corrections that account for proton and neutron density variations during the transition are considered. The nuclear diagonal and transition densities are calculated from a (quasiparticle) random phase approximation [(Q)RPA] structure model implemented with the Gogny D1S interaction. Calculated differential elastic and inelastic cross sections are mostly in very good agreement with available data. Predicted nuclear structure properties as well as scattering calculations and measurements for the yrast quadrupole excitation in $^{206}\mathrm{Pb}$ are carefully discussed. The rearrangement corrections to inelastic scattering form factors are shown to reduce medium energy nucleon inelastic cross section by up to 55%. The magnitude of these corrections changes depending on the probe, incident energy, multipolarity, and nature of the transitions considered. The combined analysis of nuclear structure properties and those for nucleon scattering cross sections measured previously over a range of incident energies provides stringent tests of present microscopic models and helps distinguish those scattering data which most likely call for revision.

Lifetimes of several short-lived excited states in Nd138 were measured with the ROSPHERE array at IFIN-HH, Bucharest, using the recoil-distance Doppler shift technique following the Sb123(F19,4n) reaction. The resulting electromagnetic transition probabilities are compared to large-scale shell model calculations and to constrained Hartree-Fock-Bogoliubov calculations with the Gogny D1S interaction, configuration mixing, and a five-dimensional collective Hamiltonian formalism. The onset of collectivity in Nd isotopes below the N=82 shell closure and the deformation induced by the alignment of protons and neutron holes in the h11/2 orbitals are discussed.

We report on the first γ-ray spectroscopy of low-lying states in neutron-rich 98,100Kr isotopes obtained from 99,101Rb(p,2p) reactions at ∼ 220 MeV/nucleon. A reduction of the 2+ 1 state energies beyond N = 60 demonstrates a significant increase of deformation, shifted in neutron number compared to the sharper transition observed in strontium and zirconium isotopes. State-of-theart beyond-mean-field calculations using the Gogny D1S interaction predict level energies in good agreement with experimental results. The identification of a low-lying (0+ 2 , 2+ 2 ) state in 98Kr provides the first experimental evidence of a competing configuration at low energy in neutron-rich krypton isotopes consistent with the oblate-prolate shape coexistence picture suggested by theory

The light krypton isotopes were studied in a series of Coulomb excitation experiments using radioactive beams at GANIL. The static quadrupole moments found in these experiments give firm experimental evidence for the shape coexistence scenario that is based on theoretical calculations and on the systematics of low-lying excited 0+ states. The experimental results are interpreted within a phenomenological two-band mixing model. Configuration mixing calculations based on triaxial Hartree-Fock-Bogolyubov calculations with the Gogny D1S effective interaction have been performed and compared to experimental data.

A fully microscopic calculation of inelastic proton scattering off {sup 208}Pb is presented, and compared to experimental scattering data for incident proton energies between 65 and 201 MeV. By constructing the nucleon-nucleus interaction through the folding of nuclear structure information with a reliable nucleon-nucleon effective interaction that has no adjusted parameter, a consistent framework is built, for probing the influence of different descriptions of nuclear structure on nucleon inelastic scattering predictions. The absence of phenomenological normalization in this framework guarantees a unique and unambiguous interpretation of our calculations in terms of quality of the underlying nuclear structure description: a feature that had been reserved, until recently, to the electron probe. This tool is used to investigate the effect of long range correlations embedded in excited states, on calculated inelastic observables, demonstrating the sensitivity of nucleon scattering predictions to details of the nuclear structure.

Two-dimensional Hartree-Fock-Bogoliubov (HFB) calculations have been performed from spherical shapes to large deformations with constraints on axial quadrupole and octupole deformations in 238 U , 256–260 Fm and 226 Th actinides. Scission configurations have then been identified in this subspace of collective coordinates and many nuclear properties of the nascent fragments have been derived, such as deformation, deformation energy or prompt neutron multiplicity. The HFB states have then served as basis states for time-dependent collective calculations based on the Time-Dependent Generator Coordinate Method and the Gaussian Overlap Approximation to derive fission fragment yields.

The 104,106,108Ru nuclei have been produced as fission fragments following the fusion reaction 28Si + 176Yb at 145 MeV bombarding energy; prompt gamma rays emitted in the reaction were detected using the Eurogam II array. Their high-spin level schemes have been obtained, particularly several side bands have been extended or newly observed. Experimental results are discussed in the framework of both collective model and the rotating mean-field approach in which the Gogny force is the sole input. These calculations provide very good descriptions of both low-spin and high-spin structures observed in the neutron-rich even-A Ru isotopes.

An outline is presented of the status of nuclear data evaluation for accelerator driven systems. The international effort consists mainly of measuring, compiling and calculating nuclear data for elements and isotopes relevant for transmutation of radioactive waste, energy amplification and other accelerator-related nuclear applications. We argue that input for global, macroscopic calculation schemes for hybrid nuclear systems basically should consist of two types of nuclear data: (a) high-energy transport codes for energies above about 150 MeV, (b) neutron and proton data libraries, for both transport and activation, for energies below about 150 MeV. Our specific contribution to the field concerns (b). The evaluated data are calculated and stored in ENDF6-format with the computer codes ECIS96, GNASH and MINGUS. New phenomenological optical model potentials up to 200 MeV are presented and we illustrate the library production with a short outline of the other employed physical methods. The calculated results are compared with the available experimental data.

A nucleon-nucleus optical model potential (OMP) is built from the nuclear matter (NM) approach of Jeukenne, Lejeune, and Mahaux (JLM). The imaginary component of the on-shell NM mass operator, originally parametrized by these authors as a function of matter density and energy, is given a new representation suitable for energies from 1 to 200 MeV. The JLM model extended in this manner is then applied through an improved local density approximation (LDA) to treat nucleon scattering from closed- and near closed-shell nuclei with masses $40l~Al~209$. For proton, neutron, and charge radial densities, we use those obtained from Hartree-Fock-Bogoliubov calculations based on the finite range, density dependent Gogny force. Several LDA and spin-orbit potential prescriptions are tested to select those which provide the best overall description of elastic scattering and reaction measurements. Over three hundred datasets including differential cross sections, analyzing powers, spin rotation functions, and reaction cross sections are considered in the present analyses. The OMP components include normalization factors which are optimized for each incident energy, probe, and for most target nuclei. We give close forms which represent the energy variation of these factors for the $n+X$ and $p+X$ systems. The global OMPs built in this manner produce a good overall description of the neutron and proton scattering and reaction measurements available up to 200 MeV.

Differential scattering cross-section data have been measured at 43 angles from ${11}^{\ifmmode^\circ\else\textdegree\fi{}}$ to ${160}^{\ifmmode^\circ\else\textdegree\fi{}}$ for 37-MeV neutrons incident on $^{209}\mathrm{Bi}$. The primary motivation for the measurements is to address the scarcity of neutron scattering data above 30 MeV and to improve the accuracy of optical-model predictions at medium neutron energies. The high-statistics measurements were conducted at the China Institute of Atomic Energy using the $^{3}\mathrm{H}$($d,n$)$^{4}\mathrm{He}$ reaction as the neutron source, a pulsed deuteron beam, and time-of-flight (TOF) techniques. Within the resolution of the TOF spectrometer, the measurements included inelastic scattering components. The sum of elastic and inelastic scattering cross sections was computed in joint optical-model and distorted-wave Born approximation calculations under the assumption of the weak particle-core coupling. The results challenge predictions from well-established spherical optical potentials. Good agreement between data and calculations is achieved at 37 MeV provided that the balance between surface and volume absorption in a recent successful model [A. J. Koning and J. P. Delaroche, Nucl. Phys. A 713, 231 (2003)] is modified, thus suggesting the need for global optical-model improvements at medium neutron energies.

We have developed microscopic models for nucleon induced inelastic scattering and one-step direct preequilibrium emission. These models are based on reliable effective in-medium two-body interactions and a microscopic description of the ground and excited states of target nuclei. No arbitrary renormalization process enters our analyzes and the predictions are directly compared to experimental data. The nuclear structure information are obtained in the Random Phase Approximation (RPA) framework with the Gogny force, which provides accurate descriptions of spherical nuclei without pairing. For medium energy (50-200 MeV) proton induced reactions, this approach gives very good predictions for direct inelastic scattering and for the first-step in direct preequilibrium emission. The one-step preequilibrium model has also been extended to fast neutron scattering (10-20 MeV) for the 90Zr target described with RPA theory, and for axially deformed nuclei with a simpler description of the excited states (i.e. particle-hole excitations). Predictions of the reaction model reproduce well experimental data for 90Zr. For deformed targets (232Th and 238U), our calculations underestimate the data at high emission energy. The cross section missing for both actinides may stem from the excitation of vibrational states with excitation energies lower than 5 MeV which are not described with incoherent particle-hole excitations. This defect might be cured if the target spectra are described within the Quasi-particle-RPA (QRPA) theory recently implemented with the Gogny force.

A systematic study of low energy nuclear structure at normal deformation is carried out using the Hartree-Fock-Bogoliubov theory extended by the Generator Coordinate Method and mapped onto a 5-dimensional collective quadrupole Hamiltonian. Results obtained with the Gogny D1S interaction are presented from dripline to dripline for even-even nuclei with proton numbers Z=10 to Z=110 and neutron numbers N less than 200. The properties calculated for the ground states are their charge radii, 2-particle separation energies, correlation energies, and the intrinsic quadrupole shape parameters. For the excited spectroscopy, the observables calculated are the excitation energies and quadrupole as well as monopole transition matrix elements. We examine in this work the yrast levels up to J=6, the lowest excited 0^+ states, and the two next yrare 2^+ states. The theory is applicable to more than 90% of the nuclei which have tabulated measurements. The data set of the calculated properties of 1712 even-even nuclei, including spectroscopic properties for 1693 of them, are provided in CEA website and EPAPS repository with this article \cite{epaps}., 51 pages with 26 Figures and 4 internal tables; this version is accepted by Physical Review C

The structure of even-even $N=40$ isotones is studied from drip line to drip line through the systematic investigation of their quadrupole modes of excitation. Calculations are performed within the Hartree-Fock-Bogoliubov approach using the Gogny D1S effective interaction. Where relevant, these calculations are extended beyond mean field within a generator-coordinate-based method. An overall good agreement with available experimental data is reported, showing that collectivity increases from the neutron to the proton drip line. Whereas $^{60}\mathrm{Ca}$ and $^{68}\mathrm{Ni}$ display a calculated spherical shape in their ground states, all other isotones show a prolate-deformed ground-state band and a quasi-$\ensuremath{\gamma}$ band. Coexistence features are predicted in the neutron-deficient $N=40$ isotones above $^{74}\mathrm{Se}$.

The constrained Hartree-Fock-Bogoliubov method is used with the Gogny interaction D1S to calculate potential energy surfaces of fissioning nuclei $^{226}\mathrm{Th}$ and $^{256,258,260}\mathrm{Fm}$ up to very large deformations. The constraints employed are the mass quadrupole and octupole moments. In this subspace of collective coordinates, many scission configurations are identified ranging from symmetric to highly asymmetric fragmentations. Corresponding fragment properties at scission are derived yielding fragment deformations, deformation energies, energy partitioning, neutron binding energies at scission, neutron multiplicities, charge polarization, and total fragment kinetic energies.

We calculate potential energy surfaces in the elongation‐asymmetry plane, up to very large deformations, with the Hartree‐Fock‐Bogoliubov method and the Gogny nucleon‐nucleon effective interaction DIS, for the 226Th and 256,258,260Fm fissioning systems. We then define a criterion based on the nuclear density, in order to discriminate between pre‐ and post‐scission configurations. Using this criterion, many scission configurations are identified, and are used for the calculation of several fragment properties, like fragment deformations, deformation energies, energy partitioning, neutron binding energies at scission, charge polarization, total fragment kinetic energies and neutron multiplicities.

GANIL E344aS; Shape coexistence in the light krypton isotopes was studied in two low-energy Coulomb excitation experiments using radioactive $^{74}$Kr and $^{76}$Kr beams from the SPIRAL facility at GANIL. The ground-state bands in both isotopes were populated up to the $8^+$ state via multi-step Coulomb excitation, and several non-yrast states were observed. Large sets of matrix elements were extracted for both nuclei from the observed $\\gamma$-ray yields. Diagonal matrix elements were determined by utilizing the reorientation effect. In both isotopes the spectroscopic quadrupole moments for the ground-state bands and the bands based on excited $0_2^+$ states are found to have opposite signs. The experimental data are interpreted within a phenomenological two-band mixing model and model-independent quadrupole invariants are deduced for the relevant $0^+$ states using the complete sets of matrix elements and the formalism of quadrupole sum rules. Configuration mixing calculations based on triaxial Hartree-Fock-Bogolyubov calculations with the Gogny D1S effective interaction have been performed and are compared both with the experimental results and with recent calculations using the Skyrme SLy6 effective interaction and the full generator-coordinate method restricted to axial shapes.

Reliable nuclear structure predictions are needed for reaction data evaluations, whenever experimental information is missing. Even if full parameter-free evaluations are not possible nowadays, some noteworthy progress in both structure and reaction fields has been accomplished recently. We present here some results on fission barriers and shape isomers partial γ-back decay and fission lifetimes. Calculations have been performed using the effective D1S Gogny force and the Generator Coordinate Method with the Gaussian Overlap Approximation based on Hartree- Fock-Bogoliubov results.

PTH; International audience; Microscopic results on fission barriers, partial gamma-back and fission lifetimes of shape isomers are presented. They have been obtained from mean-field and beyond mean-field calculations using the effective D1S Gogny force.

Structure properties of fifty five even-even actinides have been calculated using the Gogny D1S force and the Hartree-Fock-Bogoliubov approach as well as the configuration mixing method. Theoretical results are compared with experimental data., 5 pages, 5 figures, proceeding of FUSION06

The Hartree-Fock-Bogoliubov method implemented with the Gogny-D1S force and used in a systematic study of the even-even $N=16$ isotones from stability to the neutron drip line strongly suggests that a subshell gap, approximately 4 MeV wide, is opening at $N=16$. The first ${2}^{+}$ levels as well as $B(E2;{0}_{\mathrm{gs}}^{+}\ensuremath{\rightarrow}{2}^{+})$ reduced $E2$ transition probabilities have also been predicted in configuration mixing and standard random phase approximation calculations using D1S. These results compare favorably with experimental information available for the $Z=10--18$ nuclei and with expectations for $^{24}\mathrm{O}$ properties. They also fully support our mean-field predictions, namely that $N=16$ is a spherical magic number at the oxygen neutron drip line.

Differential neutron elastic scattering cross sections for {sup 12}C, {sup 40}Ca, and {sup 208}Pb have been measured using the continuum neutron source at the Los Alamos Neutron Science Center. The mean incident neutron kinetic energies ranged from 65 to 225 MeV. The large acceptance drift chamber based (n,p) recoil detector telescope spanned a center-of-mass angular range of 7 deg. to 23 deg. The measured cross sections are compared with calculations obtained with different optical model potentials, including predictions based on microscopic theory and phenomenology.

A facility for studies of elastic neutron scattering in the 50–130 MeV range has been developed. In addition to elastic neutron scattering, it has been used for (n,p) and (n,d) reaction experiments. The performance of the device has been illustrated in measurements of the (n,p) and (n,n) cross sections on 1H and 12C. Elastic neutron scattering from 12C and 208Pb has been studied at 96 MeV in the 10–70 degree interval. The achieved energy resolution, 3.7 MeV, is about one order of magnitude better than for any previous experiment above 65 MeV incident energy. The present experiment represents the highest neutron energy where the ground state has been resolved from the first excited state in neutron scattering. A novel method for normalization of the absolute scale of the cross section has been used. The estimated normalization uncertainty, 3 %, is unprecedented for a neutron-induced differential cross section measurement on a nuclear target. The results are compared with modern optical model predictions, based on phenomenology or microscopic nuclear theory. The data on 208Pb are in general in good agreement with the theory models. All theory models fail to describe the 12C data in the 30–50 degree interval, where the models predict a saddle structure not displayed by the present experimental data. Various reasons for this discrepancy have been investigated. For the other parts of the angular range studied, the agreement is good. These measurements have to a large degree been motivated by needs in various application areas, i.e., nuclear waste incineration by fast neutrons and biomedical effects caused by neutrons. The implications of the present results on these applications are discussed.

Proton reaction cross sections were measured on various stable and exotic nuclei, aiming at a better understanding of the potential for neutron rich nuclei.

The structure properties of the even-even nuclei 226, 228, 230, 232, 234Th, 230, 232, 234, 236, 238, 240U, 240, 242, 244, 246Pu, and 242, 244, 246, 248Cm have been investigated at normal and superdeformed shapes in microscopic mean-field calculations based on Gogny force. Collective levels are predicted from constrained Hartree-Fock-Bogoliubov and configuration mixing calculations. Two quasiparticle states are also predicted from blocking calculations for neutron and proton configurations. Predictions are shown and compared with experimental data at superdeformed shapes.

Differential cross sections for neutron elastic scattering and inelastic scattering to the first 2/sup +/ and 3/sup -/ excited states have been measured at 10, 14, and 17 MeV for /sup 120/Sn and at 10 and 14 MeV for /sup 116/Sn. Analyzing powers have also been measured at 10 and 14 MeV for elastic scattering from both isotopes and at 10 MeV for inelastic scattering from /sup 120/Sn. These data have been analyzed in the framework of the coupled-channels formalism for vibrational nuclei. Previously reported neutron scattering measurements performed below 25 MeV, along with total cross-section measurements from 10 keV to 100 MeV, and s- and p-wave strength functions were also considered in the analysis in order to place additional constraints on the optical potential parameters. Neutron scattering deformations have been deduced for the quadrupole and octupole vibrations. These deformations have been compared with those derived from earlier (n,n') and (p,p') scattering measurements which were reanalyzed in the present work.

Nuclear deformation of the $s\ensuremath{-}d$ shell nuclei $^{24}\mathrm{Mg}$, $^{28}\mathrm{Si}$, and $^{32}\mathrm{S}$ has been investigated by means of fast neutron scattering. Differential cross sections have been measured at the incident neutron energies of 9.76 and 14.83 MeV, over the angular range from 15\ifmmode^\circ\else\textdegree\fi{} to 160\ifmmode^\circ\else\textdegree\fi{}. Angular distributions have been obtained for the elastic scattering and the inelastic scattering to low lying collective states. The measurements have been compared to the predictions of collective models, and nuclear deformations have been determined for these nuclei. The coupled-channel and compound-nucleus formalisms were used in the calculations. The analysis shows that these nuclei exhibit quite different shapes, and confirms the oblate deformation of $^{28}\mathrm{Si}$ established in recent works. A detailed comparison of the deformations obtained in this study with those deduced from (p,p\ensuremath{'}), (d,d\ensuremath{'}), ($\ensuremath{\alpha}$,${\ensuremath{\alpha}}^{\ensuremath{'}}$), ($^{16}\mathrm{O}$, $^{16}\mathrm{O}\ensuremath{'}$), other (n,n\ensuremath{'}), and charge distribution measurements is presented and discussed. It is emphasized that for these $N=Z$ nuclei the quadrupole deformations and deformation lengths are in very good agreement when measured through neutron and proton scattering as well as electromagnetic excitations.

Differential cross sections have been measured for the scattering of 8 MeV neutrons from {sup 190,192}Os and {sup 194}Pt. These measurements have been combined with information from other neutron scattering experiments to fix accurately the electric quadrupole and octupole excitations strengths for low-lying levels. Comparison of this information with electromagnetic excitations for these same nuclei elucidates the rapidly evolving behavior of low-lying collective structures in Pt and Os nuclei. The {sup 194}Pt excitations are those of a nucleus with a potential energy surface very soft to nonaxial deformations. On the other hand, the scattering cross sections for excited levels of {sup 190}Os show evolution of excitations toward those of a nucleus vibrating about a prolate equilibrium shape.

It is shown that the dispersion relation which connects the real and imaginary central parts of the proton-nucleus optical model potential gives rise to a real Coulomb correction term ΔV c , which consists of energy dependent surface and volume components. This feature is illustrated for proton scattering from 40 Ca at energies below 40 MeV, where the surface component of ΔV c exhibits large variations with incident energy. Our findings are compared to a recent experimental determination of ΔV c .

Measurements of neutron differential scattering cross sections at 4.55 MeV, and of neutron total cross sections at low energies have been made with an isotopically enriched sample of /sup 194/Pt. These results are combined with earlier neutron scattering data measured at 2.5 MeV in a consistent set of coupled channels analyses based on the low-lying collective excitations of /sup 194/Pt. The results of these measurements and analyses extend the tests of the collective character of /sup 194/Pt, and show the strong relationship between scattering and the dynamics of nuclear excitations. We are able to discriminate amongst different models which have been offered to interpret the low-lying structure of this nucleus. Some information from an associated 8 MeV neutron scattering experiment is also included; the entire neutron data set allows us to determine that the strength of the real scattering potential has a nonlinear neutron energy dependence, and further that its geometry must be energy dependent.

Extended coupled channels calculations have been performed for neutron elastic and inelastic cross sections and analyzing powers for vibrational nuclei with 40

Differential cross sections for neutron scattering from the /sup 182,183,184,186/W isotopes have been measured at an incident energy of 3.4 MeV. Angular distributions have been obtained for elastic scattering and inelastic scattering to the first and second excited levels of the four isotopes. Nuclear deformations have been extracted for these nuclei from a coherent analysis which combines the data presented here with low energy neutron scattering properties and total cross sections over a wide energy range. The coupled-channel and compound nucleus formalisms were used in this analysis. Volume integrals and root-mean-square radii of the obtained neutron optical model potential are presented and compared to the theoretical predictions of Jeukenne, Lejeune, and Mahaux. In addition, the quadrupole and hexadecapole moments of our potential are compared to the potential moments deduced from deuteron and alpha-particle scattering measurements and to experimental charge distribution moments. Finally, matter rms radii have been estimated for the four isotopes and are compared with new Hartree-Fock-Bogolyubov calculations involving Gogny's D1 effective force.

Angular distributions of the analyzing power A/sub y/(theta) have been measured for neutron elastic scattering and for neutron inelastic scattering to the first 2/sub 1//sup +/ states of /sup 54,56/Fe and /sup 58.60/Ni at 10 MeV, and for /sup 54/Fe and /sup 58/Ni at 14 and 17 MeV. The differential cross sections sigma(theta) for the same processes were measured at 17 MeV for /sup 54/Fe and /sup 58/Ni. These measurements have been combined with other measurements of sigma(theta) and A/sub y/(theta) and also with total cross sections to form a sizable data set for incident neutron energies up to 80 MeV. This data set has been described in the context of the coupled channels formalism to determine the energy dependences of the various terms of the deformed optical potential. Some emphasis was placed on investigating the magnitude of the deformation parameter ..beta../sub so/ of the neutron spin-orbit potential and the possibility that it might be energy dependent.

A systematic study of the energy dependence of the local neutron optical potential up to 80 MeV has been performed using coupled channels analyses of a large set of neutron scattering and reaction observables.

While the inelastic scattering of high energy hadrons is commonly used for the study of giant resonances in nuclei, it is just recently that one has thought to take into account these states in the analysis of proton scattering at low incident energies (E ≲ 50 MeV). Feedback of coupling to giant resonances on optical model predictions are investigated for fast neutron elastic and inelastic scattering from vibrational nuclei and for neutron strength functions S0 and S1.

Elastic and inelastic proton scattering has been measured in inverse kinematics on the unstable nucleus ${}^{40}\mathrm{S}$. A phenomenological distorted wave Born approximation analysis yields a quadrupole deformation parameter ${\ensuremath{\beta}}_{2}=0.35\ifmmode\pm\else\textpm\fi{}0.05$ for the ${2}_{1}^{+}$ state. Consistent phenomenological and microscopic proton scattering analyses have been applied to all even-even sulfur isotopes from $A=32$ to $A=40$. The second analysis used microscopic collective model densities and a modified Jeukenne-Lejeune-Mahaux nucleon-nucleon effective interaction. This microscopic analysis suggests the presence of a neutron skin in the heavy sulfur isotopes. The analysis is consistent with normalization values for ${\ensuremath{\lambda}}_{v}$ and ${\ensuremath{\lambda}}_{w}$ of 0.95 for both the real and imaginary parts of the Jeukenne-Lejeune-Mahaux potential.

Experiment was performed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University; Background: The self-conjugate nuclei of the A ∼ 70 mass region display rapid shape evolution over isotopic or isotonic chains. Shape coexistence has been observed in Se and Kr isotopes reflecting the existence of deformed subshell gaps corresponding to different shell configurations. As and Ge isotopes are located halfway between such deformed nuclei and the Z = 28 shell closure. Purpose: The present work aims at clarifying the low-lying spectroscopy of 66Ge and 67As, and providing a better insight into the evolution of collectivity in light even-even Ge and even-odd As isotopes. Methods: We investigate the low-lying levels and collectivity of the neutron deficient 67As and 66Ge through intermediate-energy Coulomb excitation, inelastic scattering, and proton knockout measurements. The experiment was performed using a cocktail beam of 68Se, 67As, and 66Ge nuclei at an energy of 70-80 MeV/nucleon. Spectroscopic properties of the low-lying states are compared to those calculated via shell model with the JUN45 interaction and beyond-mean-field calculations with the five-dimensional collective Hamiltonian method implemented using the Gogny D1S interaction. The structure evolution of the lower-mass Ge and As isotopes is discussed. Results: Reduced electric quadrupole transition probabilities B(E2) have been extracted from the Coulombexcitation cross sections measured in 66Ge and 67As. The value obtained for the B(E2; 0+ 1 → 2+ 1 ) in 66Ge is in agreement with a recentmeasurement, ruling out the existence of aminimum at N = 34 in the B(E2) systematics as previously observed. New transitions have been found in 67As and were assigned to the decay of low-lying negative-parity states.

A semimicroscopic, Lane-consistent optical model is established up to 200 MeV for nucleons incident on spherical and near-spherical nuclei with masses $40l~Al~209.$ This model, based on the earlier approach of Jeukenne, Lejeune, and Mahaux in nuclear matter, is an extension of our previous work [E. Bauge, J. P. Delaroche, and M. Girod, Phys. Rev. C 58, 1118 (1998)]. The modulus of the isovector potential is extracted and compared with measurements and fully microscopic predictions. Good overall descriptions of nucleon scattering, of transitions to isobaric analog states, and of reaction observables are obtained down to 1 keV. Those results are discussed in detail.