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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 random phase approximation (RPA) long-range correlations are known to play a significant role in understanding the depletion of single particle-hole states observed in ($e,{e}^{'}$) and ($e,{e}^{'}p$) measurements. Here the RPA theory, implemented using the D1S force is considered for the specific purpose of building correlated ground states and related one-body density matrix elements. These may be implemented and tested in a fully microscopic optical model for NA scattering off doubly closed-shell nuclei. A method is presented to correct for the correlations overcounting inherent to the RPA formalism. One-body density matrix elements in the uncorrelated (i.e., Hartree-Fock) and correlated (i.e., RPA) ground states are then challenged in proton scattering studies based on the Melbourne microscopic optical model to highlight the role played by the RPA correlations. Agreement between the parameter free scattering predictions and measurements is good for incident proton energies ranging from 200 MeV down to approximately 60 MeV and becomes gradually worse in the lower energy range. Those features point unambiguously to the relevance of the g-matrix method to build microscopic optical model potentials at medium energies, and emphasize the need to include nucleon-phonon coupling, that is, a second-order component of the Feshbach type in the potential at lower energies. Illustrations are given for proton scattering observables measured up to 201 MeV for the $^{16}\mathrm{O}$, $^{40}\mathrm{Ca}$, $^{48}\mathrm{Ca}$, and $^{208}\mathrm{Pb}$ target nuclei.

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.

Coupled-channel and dispersive-optical model analyses of published neutron scattering and reaction data for {sup 27}Al, {sup 59}Co, and {sup 93}Nb at incident energies between 0.1 and 80 MeV have been performed. The resulting potentials are used to place constraints on the determination of the spin-spin interaction from published spin-spin cross-section measurements. For the three nuclei, the strength of the central real spin-spin potential, which was taken to have a surface plus volume shape, was found to be small. Volume integrals for this central potential component were determined to be in the 4-7 MeV fm{sup 3} range and to decrease somewhat as mass number increases.

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.

Proton reaction cross-section measurements on various stable and neutron-rich nuclei (He-4,He-6, Li7-9, Be9-11, F21-24, N22-26, Na25-29 and Mg29-32) were performed via the attenuation method at intermediate energies (similar to 35-75 A MeV) and using a cryogenic hydrogen target. The results are discussed in the framework of different approaches of the nucleon-nucleus potential. (C) 2002 Elsevier Science B.V. All rights reserved. Nuclear Physics A

Measurements of elastic and inelastic scattering cross sections have been performed for 2.5 and 4.1 MeV neutrons incident on ${}^{155,156,157,158,160}\mathrm{Gd}.$ Angular distributions have been measured at both energies for the ${0}^{+},$ ${2}^{+},$ and ${4}^{+}$ members of the ground-state (gs) band of the even-even isotopes and for the ${3/2}^{\ensuremath{-}},$ ${5/2}^{\ensuremath{-}},$ and ${7/2}^{\ensuremath{-}}$ levels of the gs band of the even-odd isotopes. Angular distributions for inelastic scattering from the ${9/2}^{\ensuremath{-}}$ level of the gs band of ${}^{155}\mathrm{Gd}$ and ${}^{157}\mathrm{Gd}$ have also been measured at 4.1 MeV. These results together with previously measured s- and p-wave strength functions, potential scattering radii, and elemental total cross sections have been combined in an analysis based on coupled-channel semimicroscopic optical model potential (OMP) and statistical model calculations. The deformed OMP, an extension of our earlier work [E. Bauge, J.P. Delaroche, and M. Girod, Phys. Rev. C 48, 1118 (1998)], is built using a complex density-dependent effective interaction and deformed matter densities deduced from unconstrained, axially symmetric Hartree-Fock-Bogoliubov (HFB) calculations based on the Gogny force. The HFB calculations which describe quite nicely a wealth of results from electron scattering and Coulomb excitations measurements, lead to semimicroscopic OMP predictions in good agreement with the neutron scattering and reaction measurements. A phenomenological OMP analysis is also performed to compare the global properties of both potentials.

A quantal Hamiltonian ${\stackrel{^}{\mathcal{H}}}_{\mathrm{coll}}$ expressed in terms of the five collective quadrupole coordinates is built for eight nuclei ${(}^{190,192,194}$Hg, ${}^{192,194,196}$Pb, and ${}^{196,198}$Po) which display secondary minima at large elongation in their potential energy surface. These surfaces as well as the tensor of inertia entering ${\stackrel{^}{\mathcal{H}}}_{\mathrm{coll}}$ are deduced from constrained Hartree-Fock-Bogoliubov calculations based on Gogny force. A two-center basis method employed to solve ${\stackrel{^}{\mathcal{H}}}_{\mathrm{coll}}$ is presented. The stability of predicted collective spectra is discussed. Yrast and vibrational $\ensuremath{\pi}=+$ superdeformed (SD) bands are predicted together with collective bands at normal deformation (ND). The predicted yrast SD bands at low spin display properties which compare favorably with experimental information. Quite good agreement is in particular obtained for the isomeric energies of nuclei for which the link between SD and ND levels is experimentally known. Among the excited SD bands which are here predicted, those built on top of $\ensuremath{\beta}$ vibrations are lower in energy. Only for the ${}^{196,198}$Po isotopes are these excitation energies falling in the low energy range $E\ensuremath{\sim}$0.8--1.0 MeV. These properties should favor an experimental discovery of $\ensuremath{\beta}$-vibrational SD bands in the $A\ensuremath{\sim}$190 mass region.

In the framework of microscopic models, we present two methods for describing superdeformed (SD) band properties. The first one is the cranked Hartree-Fock-Bogoliubov (HFB) method, without and with inclusion of particle number projection. The second one is the Gaussian overlap approximation to the generator coordinate method (GCM+GOA) with whichwetreat the five quadrupole collective coordinates. Both methods use the Gogny force. Moments of inertia and excitation energies of SD bands are calculated and compared with experimental results.

A systematic study of low energy nuclear structure at normal deformation has been carried out using the Generator Coordinate Method mapped onto a 5-Dimensional Collective quadrupole Hamiltonian (5DCH) by using the Gaussian Overlap Approximation (GCM-GOA). The collective space is spanned by Hartree Fock Bogoliubov (HFB) states under axial and triaxial quadrupole constraints deduced with the D1S Gogny force. In addition, our 5DCH includes the Thouless-Valatin dynamical corrections to its rotational kinetic terms. The work is described in detail elsewhere together with the corresponding comparisons with experimental data when it is available. Many properties show a satisfactory agreement with experiment, but there is an almost systematic overestimation of vibrational band head energies, which is the subject of the present paper. We show here the performance of the theory on related observables, and propose improvements of the theory to address the problem of the vibrational band heads. An important reason for the deficient is the treatment of vibrational inertial parameters. In particular, the theory needs to include the dynamical Thouless-Valatin corrections to the vibrational terms in the 5DCH. In present work, on the aim of a simple formula grounded by known symmetry rules within the 5DCH, these dynamical TV corrections are roughly estimated, allowing us to handle their possible effects in term of spectroscopic properties, to present a guess of the next model improvment, and to isolate some areas in the chart where states Inπ = 0+2, 2+2 or 2+3 seem to have important components out of the scope of a pure collective quadrupole approach.

A large number of superdeformed (SD) bands has been observed in the mass 190-region, some of which showing nearly identical γ -ray transition energies. This has been illustrated for instance in 194Hg by Cullen et al.1 More recently, some measurements indicated that octupole correlations might exist in the superdeformed nucleus 193Hg. Thus, both quadrupole and octupole collective modes may play a key role in explaining the observed SD band features in this mass region. These issues are discussed in the present work.

A completely microscopic approach of deformation and superdeformation in nuclei based on the constrained mean field theory is presented, together with applications to three Mercury isotopes. The Hartree‐Fock‐Bogolyubov theory of nuclear structure is employed with the D1S effective interaction in order to derive potential energy surfaces and associated inertia. Collective coordinates of β−γ and q20−q30 types are envisaged in this study. Collective states are computed by diagonalizing a collective Hamiltonian whose form is deduced from the Generator Coordinate theory. Well‐localized shape isomers are found in 190Hg, 192Hg and 194Hg at excitation energies 4.4, 5.4, and 6.9 MeV, respectively. Computations of all levels up to spin 22 reveal the existence of three superdeformed bands in 192Hg. B(E2)’s for both in‐band and off‐band transitions are obtained. They compare well with available measurements. The decay out of these bands is also discussed. A coupled quadrupole‐octupole collective calculation around th...

Elastic scattering cross sections have been measured for 8, 10, and 24 MeV neutrons incident on /sup 90/Zr. These measurements, together with other neutron elastic scattering and total cross section data available up to 29 MeV, are used in grid searches to obtain an optical model potential which contains a dispersion relation term. This potential is then extrapolated toward negative energies to predict bound single-particle state properties. An overall good description of the data at positive and negative energies is achieved.

Analyzing powers A/sub y/(theta) for inelastic scattering of 10-MeV neutrons to the first excited states of /sup 54/Fe, /sup 56/Fe, /sup 58/Ni, /sup 60/Ni, /sup 120/Sn, and /sup 208/Pb have been measured at a few selected angles. These data were analyzed using a coupled channels code in which the full Thomas form of the spin-orbit potential is assumed. The magnitudes of the observed spin-orbit deformations, which were found to be similar to those for (p,p') in each case, contradict recent suggestions based on microscopic nuclear structure considerations.

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 .

Differential cross sections for neutron scattering from 58 Ni and 60 Ni to the ground state and first excited state have been measured at 8, 10, 12 and 14 MeV. In addition, analyzing powers were measured for scattering to the same states for 58 Ni at 10 and 14 MeV, and for 60 Ni at 10 MeV. The data were analyzed in the framework of a coupled-channel formalism in which the vibrational model was assumed with deformed central and spin-orbit potentials. A spherical-optical-model analysis of the elastic scattering data was also performed following the coupled-channel analysis. Predictions for (p, p) and (p, p') scattering observables have been made and compared with measurements previously published. This approach permits neutron and proton deformation parameters to be deduced similarly from (n, n') and (p, p') scattering measurements for 58,60 Ni. These deformation parameters are compared in the framework of the core-polarization model of Madsen, Brown and Anderson.

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

Angular distributions of the analyzing power ${A}_{y}(\ensuremath{\bigominus})$ have been measured for elastic scattering of neutrons from $^{54}\mathrm{Fe}$ and $^{65}\mathrm{Cu}$ at 10 and 14 MeV and for inelastic scattering to the first ${2}^{+}$ state of $^{54}\mathrm{Fe}$ at 10 MeV. We have combined the results with previous measurements and analyses of the differential cross sections in the same energy range and have carried out new deformed optical model calculations where the major concern was to study the spin-orbit interaction. The need for an imaginary spin-orbit term ${W}_{\mathrm{SO}}(r)$ is discussed. The (n, n\ensuremath{'}) data are important in reducing an ambiguity found between the deformation ${\ensuremath{\beta}}_{\mathrm{SO}}$ of the real spin-orbit potential and the strength ${W}_{\mathrm{SO}}$ of the imaginary spin-orbit potential.

Elastic and inelastic scattering cross sections and analyzing powers have been determined for 16 MeV polarized protons incident on /sup 116,120,124/Sn. Data extracted for these isotopes include scattering from the lowest 2/sup +/ and 3/sup -/ collective states and two other less collective states (5/sup -/,4/sup +/) below 3 MeV in excitation. Our analysis of the data uses a coupled-channel formalism based on the harmonic vibrational model with a (0/sup +/,2/sup +/,3/sup -/,5/sup -/4/sup +/) coupling scheme. Nuclear deformation parameters of the central and spin-orbit potentials for the excited states have been extracted and compared with similar quantities deduced from (n-arrow-right,n) scattering from the same isotopes.

Real surface and volume terms, as determined from a dispersion relation, are incorporated in new optical model analyses of ( n , n) scattering from 40Ca over a broad energy range. The energy dependence of these terms lead to a rather good description of available analyzing power measurements. In contrast to previous analyses, a positive imaginary spin-orbit interaction is not needed to fit the data.

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.

Coupled-channel analyses of new (n,n') and existing (p,p') as well as (..cap alpha..,..cap alpha..') scattering measurements for the second 0/sup +/ state (1.761 MeV) in /sup 90/Zr are described. Macroscopic form factors are assumed for the E0 and E2 transitions. Multistep E2 transitions are found to dominate the direct inelastic excitations. Compound (n,n') and (p,p') scattering processes are also found to be important at incident energies up to 16 MeV. A rather good description of shapes and magnitudes of the differential cross sections is achieved.

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.

Structure studies based on either the Strutinsky method or self-consistent Hartree-Fock (HF) and Hartree-Fock-Bogoliubov (HFB) mean field theories suggest that superdeformed (SD) states might well develop at large quadrupole deformation (i.e. β ⩾0.5) in mercury isotopes. In this work, we predict the existence of I π =0 + shape isomers which might take place at excitation energies of 4.4, 5.4 and 6.9 MeV in 190 Hg, 192 Hg and 194 Hg, respectively. These SD levels are obtained by solving the Griffin-Hill-Wheeler equation in the gaussian overlap approximation. Inputs for that collective hamiltonian are tensors of inertia as well as potential energy surfaces which are deduced from constrained HFB calculations based on the finite-range, density-dependent effective force of Gogny.

Secondary minima in the potential-energy surfaces of even-even nuclei are searched for through nonaxial Hartree-Fock-Bogoliubov calculations based on a finite-range, density-dependent effective force. This study covering the mass region 64/lt//ital A//lt/208 is intended to select nonfissile nuclei which would develop shape isomers. Results are presented for nuclei which seem to be the most interesting candidates for experimental investigations.

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.

Differential cross sections \ensuremath{\sigma}(theta) and analyzing powers ${A}_{y}$(theta) for neutron scattering to the ground and first ${3}^{\mathrm{\ensuremath{-}}}$ excited state of $^{40}\mathrm{Ca}$ have been measured in the energy range from 11 to 17 MeV. Elastic and inelastic scattering measurements have been obtained for ${A}_{y}$(theta) at energies of 11.0, 13.9, and 16.9 MeV, the inelastic scattering data representing the first (n,n') measurements of ${A}_{y}$(theta) for this nucleus. Differential cross sections for (n,n) and (n,n') have been obtained at 13.9 and 16.9 MeV. Both the \ensuremath{\sigma}(theta) and ${A}_{y}$(theta) data at 13.9 MeV have been compared with previous measurements at this energy and the agreement is good, typically within less than 3%. These results have been combined with other \ensuremath{\sigma}(theta) and ${A}_{y}$(theta) data and total cross section ${\ensuremath{\sigma}}_{T}$ measurements to form a large set of scattering and reaction data for incident energies up to 80 MeV. This data set, along with \ensuremath{\sigma}(theta) and ${A}_{y}$(theta) measurements available for proton scattering in this energy range, has been described in the framework of the coupled-channel formalism. This highly constrained analysis has led to a precise determination of geometries, energy dependencies, and deformation parameters. Further analyses, which dealt with simultaneous couplings to low- and high-energy excited states, have led to improved descriptions of the elastic scattering measurements for \ensuremath{\sigma}(theta) and ${A}_{y}$(theta) at backward angles. These results confirm that real and virtual excitations of giant resonances cannot be ignored in the description of the reaction mechanism. In this context, it has also been found that corrections to the real central potentials, as estimated by Mahaux and Ngo^ from dispersion relations, help to further improve the fits to elastic scattering observables.

This theoretical work represents the first stage in our efforts to establish an extensive list of nonfissile even-even nuclei located inside or near the valley of stability which might develop shape isomers. Our selection relies upon whether a secondary minimum takes place along an elongation axis in the potential energy surfaces of nuclei spread over the mass region A

As an extension of a previous report on fast neutron scattering from the first and second excited states of 182,184,186W, we have investigated the question of the importance of direct interaction of neutrons with β− and γ− band levels of these nuclei. For that purpose we have performed new coupled channel calculations using extended coupling bases and collective wave functions from the Rotation-Vibration and Kumar and Baranger Models. The predictions are compared with recent scattering data obtained at incident energies below 4 MeV.

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.