W.G. Love

Effective quasiparticle G-matrix interaction

Abstract A derivation of the operator structure of the Brueckner G -matrix is presented. This method is used to extract¦an effective interaction based on a G -matrix in nuclear matter derived from a one-boson-exchange potential. Effects of Pauli blocking and short-range correlations have been analyzed, showing that they are essentially restricted to 1 S 0 and 3 S 1 - 3 D 1 states. The reason why the tensor force is not significantly affected by correlations is also discussed. A momentum transfer and density-dependent interaction has been constructed which may be used as a basic ingredient of the full particle-hole interaction to describe the low-lying excited states of nuclei. For further convenience, this interaction has been parametrized in terms of Yukawa-type expressions, which reproduce the exact values within 0.2% in the range of 0–2 fm −1 of momentum transfer. Based on the analysis of an analytical G -matrix, a simple functional form for the density dependence is suggested which provides an excellent fit (within 1%) in the range of the density of 0.35 ϱ 0 ⩽ ϱ ⩽ ϱ 0 . G -matrix interactions based on several phase-shift-equivalent NN potentials are considered in the Landau limit and they show a considerable sensitivity to these potentials. The results can be understood within the context of a very simple model and this provides a better understanding of different channels of the G -matrix interaction, especially those which are relatively poorly understood.

The scattering of elementary probes from nuclei at medium energy: A new look at the nucleus

Abstract A summary of the essential elements in the single scattering description of electron, pion, and proton-nucleus scattering is presented and some indication of the usefulness of these single scattering ideas in describing experimental data is given. The purpose is to delineate the basic spectroscopic features of the three reactions and provide a basis for the discussion of new information on nuclear structure that is being obtained through their use. Most notable is the observation of new spin-flip modes of nuclear excitation. Both low and high spin excitations of this type have been observed and the data is providing us with the first definitive measure of the spin-dependent coupling in nuclei over a wide range of multipolarity. Also interesting are the observation of large proton-neutron differences and new instances of Coulomb mixing in select nuclear transitions and the potential for gaining accurate information on neutron distributions in nuclear ground states and strongly correlated low lying collective excitations. Some comments on the current status of the search for manifestations of precritical phenomena in inelastic electron and proton scattering are also made.

6Li scattering: A failure of the double-folded potential model

Abstract Data for 6 Li scattering elastically from various nuclei were analyzed using the double-folding model together with a recently introduced “realistic” effective interaction which has reproduced the potentials for heavier ions. However, it is concluded that the potential for 6 Li is not given by this model which systematically overestimates it by nearly a factor of two.

Inelastic excitation of normal parity levels in 208Pb by 135 MeV protons

Abstract New cross section data for the inelastic excitation of normal parity levels in 208Pb with spins ranging from J=2 to J =2 are reported. The data are examined in terms of the collective model including deformed spin-orbit coupling. The experimental differential cross sections exhibit a striking transition from central dominated shapes to spin-orbit dominated shapes at J=8.

Density-dependent interactions and the folding model for heavy-ion potentials☆

Abstract It is pointed out that the failure of the single-folding model to predict the correct real part of heavy-ion optical potentials is partially due to the omission of effects arising from any density dependence present in the underlying nucleon-nucleon interaction. An estimate is made of the error introduced in typical calculations.

A test of the DWIA at 135 MeV using the 207Pb(p, p′) reaction

Abstract Data for the excitation of the strongly collective octupole doublet in 207Pb at EX = 2.64 MeV is used to test the distorted wave impulse approximation (DWIA) at a proton bombarding energy of 135 MeV. A complex, effective local interaction derived from the nucleon-nucleon phase shifts is used together with the wave functions of Ring and Speth for the low-lying octupole state in 208Pb. The DWIA (including central and spin-orbit terms) is found to be in reasonable agreement with both the magnitude and shape of the observed cross section.

The 90,92Zrd(p,p′) reactions at Ep = 800 MeV+

Abstract Angular distributions of analyzing powers and differential cross sections have been measured for elastic and inelastic scattering of 800 MeV protons from 90 Zr and 92 Zr. The data have been interpreted using both the collective-model distorted-wave Born approximation and the semimicroscopic distorted-wave impulse approximation with the Love and Franey t -matrix. Clear differences in the data for transitions to both the 2 + 1 and the 4 + states in the two nuclei, attributable to differences in the microscopic structures of the states, have been observed. These differences are only partially explained by the semimicroscopic analyses. Interpreting the A y data with the help of recent data-to-data relations suggests that the free L · S interaction used at 800 MeV is incorrect.

Microscopic description of normal parity excitations in the 208Pb(p, p′) reaction at 135 MeV and the shape of the nucleon-nucleon interaction

Abstract A microscopic study of new 135 MeV inelastic proton scattering data for the excitation of normal parity levels in 208 Pb with spins covering the range J =2 to 10 is reported. The short range repulsion in the central nucleon-nucleon interaction results in small central contributions to the cross sections for the transitions with J =8 and 10.

Evidence for the importance of the nucleon-nucleon spin-orbit interaction in the inelastic excitation of high spin states in 90Zr☆

Abstract A microscopic calculation of the inelastic scattering of 61.2 MeV protons to the 6+ and 8+ states in 90Zr has been carried out which includes the central, tensor and spin-orbit parts of the nucleon-nucleon interaction. The two-body spin-orbit force is found to play an important role in exciting these high spin states.

Excitation of isovector monopole and quadrupole giant resonances in 90Zr(n,p) at 65 MeV

Abstract The 90 Zr(n,p) 90 Y reaction at 65 MeV has been studied over a wide range of angles down to 0°. The data confirm the isovector monopole giant resonance recently observed in (π ± ,π 0 ) data. In addition, the data together with an RPA-DWA analysis provide evidence for the T +1 isospin component of the isovector quadrupole giant resonance and for a new giant resonance, the spin monopole, both centered near Q np =−21 MeV .