G. J. Nijgh

Scattering of polarized protons by iron and nickel isotopes

Abstract Elastic and inelastic scattering of polarized protons ( E = 17.2, 20.4, 24.6 MeV) by 54, 56 Fe and 58, 60, 62 Ni have been investigated. Most data can be readily accommodated by standard optical-model and DWBA procedures, including full Thomas coupling. The 2 + 1 state (1.41 MeV) in 54 Fe is peculiar because the inelastic scattering data require deformation parameters for the central and spin-orbit parts of the nuclear potential that differ by a factor 2 to 3; moreover, this anomaly shows a marked energy dependence.

Scattering of polarised protons by Ni, Sr, Cd, In and Sn isotopes. II. Inelastic scattering-collective analysis

For pt.I see ibid., vol.15, no.2, p.181 (1989). Inelastic scattering of polarised protons (Ep=20.4, 24.6 MeV) by 60,64Ni, 86,88Sr, 110,112,114Cd, 115In and 116,118,120,122,124Sn has been investigated. Except for the case of 60Ni, only for the 21+ and 31- states could statistically reliable data be obtained. The data have been analysed with the DWBA employing a collective form factor. The agreement between experiment and theory is fairly good, although the experimental data tend to exhibit somewhat more structure than the theory predicts. For 60Ni also data for higher excited states have been obtained. These have been analysed with moderate success by coupled-channels calculations. The deformation parameters found for the Sn isotopes can be described in terms of the IBA model. Some suggestions for the applications of the IBA model in inelastic scattering are given.

Scattering of polarised protons by Ni, Sr, Cd, In and Sn isotopes. I. Elastic scattering

Elastic scattering of polarised protons (E=20.4, 24.6 MeV) by 60,64Ni, 86,88Sr, 110,112,114Cd, 115In and 116,118,120,122,124Sn has been investigated. Most data can be readily accommodated by standard optical-model fitting procedures. The isospin dependence of the optical potential determine from a series of isotopes does not always follow the general trends of the global potentials.

Scattering of 20.4 MeV polarized protons from even-mass zinc isotopes

Measurements are reported on polarized-proton scattering from the even-mass zinc isotopes at 20.4 MeV beam energy. The elastic and first-order inelastic processes are represented well by standard theory. The analysis of the two-phonon multiplets presents difficulties which may indicate a change in the nuclear structure between isotopes or the occurrence of an energy-dependent interference process.

Scattering of 22.3 MeV polarized protons from the even-mass cadmium isotopes 106-116Cd

Measurements have been done on polarized-proton scattering from the even-mass cadmium isotopes 106-116Cd, at a beam energy of 22.3 MeV. The experimental data were analysed using first- and second-order vibrational models in a coupled-channels formalism. The 01+, 21+ and 31- levels are represented satisfactorily by theory. In 106-116Cd the 22+ and 41+ levels were resolved; for the 22+ levels the theory systematically underestimates the first diffraction maximum of the cross section at 30 degrees while the 41+ levels are reproduced reasonably well. In 112-114Cd the 02+ level could also be studied; there are indications for a strong coupling between the two-phonon 0+ state in the ground-state band and the 0+ head of the intruder band. In 114Cd we also investigated the 23+ level, probably the first excited state of the intruder system, which showed an angular pattern with more pronounced details than the 21+ states. Finally in 112Cd the 11

Scattering of 21.1 MeV polarized protons from 89Y

and 51- levels were studied which have a strong direct coupling to the ground state.

Polarized-proton scattering by even-mass germanium and selenium isotopes at 22 MeV incident energy

Abstract The elastic and inelastic scattering of 21.1 MeV protons from 89Y have been investigated. The excited states with a collective nature can be described quite well with standard OM and DWBA techniques. The transitions to the low-lying single-particle states are described with antisymmetrized microscopic DWBA including tensor and spin-orbit forces. The agreement with the experimental data is encouraging.

The (p,d) reaction on 56Fe at 24.6 MeV

Elastic and inelastic scattering of 22.3 MeV polarized protons from even-mass nuclides 70-76Ge and 76-80Se has been studied. The elastic data have been analysed by optical-model techniques; also the elastic and inelastic data together have been investigated using a coupled-channels formalism. In the latter case the original optical-model parameters had to be modified in order to obtain an adequate description of the elastic scattering process. The 21+ and 31- states are described satisfactorily by the coupled channels formalism in a vibrational model. This model represents the 02+ states better than expected, and the 22+ and 41+ states only if the 2+ and 4+ levels are treated as mixtures of one-phonon and two-phonon components. Alternatively, a rotational description of the 21+, 22+ and 41+ states was moderately successful. Some features may be understood qualitatively from the interacting-boson approximation (IBA-2).

The (p,d) reaction on 58Ni and 56Fe at 24.6 MeV

The authors have studied the (p,d) reaction on 56Fe, initiated by a 24.6 MeV polarised proton beam. Cross sections and analysing powers were obtained for nine states in the final nucleus 55Fe. These were compared with DWBA and CRC calculations, confirming spin and parity assignments. As opposed to the situation in 58Ni(p,d) no large two-step contributions were necessary for obtaining agreement with calculations.

Study of multistep processes in the reaction 116Sn(p, t)114Sn AT 25.1 MeV

The (p,t) reaction on 56Fe and 58Ni initiated by 24.6 MeV polarised protons has been investigated. The reaction process is described in terms of simultaneous and sequential neutron transfer. For all five final states studied the sequential process competes strongly with simultaneous transfer of a neutron pair. Theoretical values for the spectroscopic amplitudes were derived from shell-model wavefunctions; these seem to give a reliable description of the reaction process.