B.W. Ridley

Isospin dependence of the mass-3 optical potential from the comparison of triton and 3He elastic scattering

Abstract Differential cross sections have been measured for the elastic scattering of 21 MeV 3 He particles by 40 Ca, 52 Cr, 54 Fe, 62 Ni, 64 Ni, 90 Zr, 92 Zr, 94 Zr and 118 Sn. These data are compared with recently published 20 MeV triton elastic scattering data for the same targets in a simultaneous optical-model analysis. The strength of the isospin contribution to the optical potential obtained from the elastic scattering studies is compared with that required to describe ( 3 He, t) quasi-elastic scattering data. The major part of the asymmetry dependence previously observed in triton optical potentials is shown to be unrelated to isospin.

The energy-loss spectrograph at the university of colorado cyclotron☆

Abstract A spectrograph system has been developed to satisfy both the requirements of high resolution charged particle spectroscopy and those of neutron time-of-flight spectroscopy. In the charged particle mode the instrument is an energy-loss spectrograph with a fractional energy resolution of 3 × 10−4, while in the neutron time-of-flight mode a resolution of 40 keV is achieved with low background at a neutron energy of 16 MeV. The novel feature of the spectrograph is that the charged particle and neutron analyzing systems are both fixed in position with the reaction angle varied by rotation of the beam preparation system.

Energy dependence of the optical model parameters for α-particles scattered from 40Ca and 58Ni☆

Abstract The differential cross sections for the elastic scattering of 3 He ions on targets of 40 Ca and 58 Ni have been measured at incident energies of 27.7, 51.4, 73.2 and 83.5 MeV. The results of optical model analyses showed that only one unique potential ( J R ≈ 330 MeV · fm 3 ) with a surface absorptive term can provide acceptable fits to the large angle elastic scattering cross sections at 83.5 MeV. The particular geometrical set found at 83.5 MeV could not, however, give an adequate fit to the data with energy less than 40 MeV. Subsequent analyses indicated that a break in the energy dependence of the real potential is observed for the low energy data. Explicit energy dependent terms were obtained by fitting all the data simultaneously. These phenomenological potentials were also compared with the folded nucleon-nucleus potential. The influence of the α-particle channels on the elastic scattering of 3 He ions at 83.5 MeV was also examined.

The 96Zr(p, p′) and 96Zr(p, d) reaction at 19.4 MeV

Abstract Elastic and inelastic scattering measurements with 19.4 MeV protons from 96Zr have been performed. The angular distributions for seven inelastic proton groups have been compared to distorted wave calculations using both collective and shell-model form factors. Angular distributions for 11 deuteron groups were measured and compared to distorted wave calculations using a local, zero-range theory. Pick-up of 2 d 5 2 , 1 g 9 2 and 3 s 1 2 neutrons was observed and spectroscopic factors determined.

Optical-model analysis of 38 MeV 3He elastic scattering extended into the backward hemisphere

Abstract Angular distributions for 3He elastic scattering, have been measured to 155° at 37.7 MeV on 48Ti, 58Fe and 90Zr, and at 36.8, 37.4, 37.5 and 38.1 MeV on 58Ni. These have been analysed in terms of the optical model. Ambiguities in the real well depth and in the geometrical form of the imaginary potential have been studied. The usefulness of a surface-peaked imaginary potential, particularly in fitting the backward angle data, is indicated by these analyses. The utility of a spin-orbit term in fitting large angle data was investigated. Multiset fits were performed to the data. No conclusions concerning the necessity of either an isospin or asymmetry term in the optical potential at these energies could be drawn. Other information gained from extending 3He elastic scattering measurements into the backward hemisphere is discussed.

A study of the excited states of 57Ni via the (p, d) AND (3He, α) reactions at 27.5 and 37.7 MeV

Abstract The excited states of the 57 Ni nucleus have been studied using the neutron pick-up reactions 58 Ni(p, d) 57 Ni and 58 Ni( 3 He, α) 57 Ni at energies of 27.5 and 37.7 MeV respectively. Recently reported levels at 2.45, 3.01 and 3.36 MeV are confirmed and new levels are reported at 4.46, 4.71, 5.86, 8.24 and 8.79 MeV. Spectroscopic factors and l n , J and T assignments are made for most levels. Previously unreported l n = 0 and 2 levels are discussed.

A study of the 106Pd(p, d)105Pd and 106Pd(3He, d)107Ag reactions

Abstract The 106 Pd(p, d) 105 Pd reaction has been studied at 22.9 MeV with an energy resolution of 13 keV. Angular distributions permitted the assignment of l -values and the extraction of spectroscopic factors for 13 states including several previously unresolved l = 2 transitions. The 106 Pd( 3 He, d) 107 Ag reaction has also been studied at 32.8 MeV with a resolution of 20 keV. Angular distributions were obtained, l -values assigned and spectroscopic factors extracted for 14 levels including many not observed previously in a proton transfer reaction. The level structure of 105 Pd and 107 Ag is discussed particularly in terms of quasirotational bands.

Global optical-model analysis of 37.7 MeV 3He elastic scattering from medium-A nuclei (46 ≦ A ≦ 91)

Abstract Differential cross sections have been measured for the elastic scattering of 37.7 MeV 3 He particles by 46 Ti, 50 Ti, 51 V, 62 Ni and 91 Zr. These data together with previously reported data on 48 Ti, 58 Fe, 58 Ni and 90 Zr have been analysed m terms of the optical model. Results of fits to the individual angular distributions are presented. The emphasis, however, is put on the results of global fits. Good fits are obtained by assuming that either all OM parameters or only the geometrical parameters are the same for each nucleus. These fits proved rather insensitive to dependencies of the well depths on isospin, asymmetry and energy. A preference for a surface-peaked imaginary potential rather than the usual volume shape has been observed throughout this study.

Inelastic proton scattering from 42Ca and 44Ca and analysis in terms of shell-model form factors

Abstract Inelastic proton scattering measurements have been carried out at 22.9 MeV from 42 Ca and 44 Ca. Angular distributions have been measured for 11 inelastic proton groups from 42 Ca and eight from 44 Ca. The experimental differential cross sections have been compared with distorted wave calculations using a collective-model interaction in which both the real and imaginary terms of the optical potential were deformed. Extensive comparisons are performed with distorted wave calculations using a shell-model description for the nuclear states as well as more complicated wave functions with a collective component. An empirical core polarization correction is used. The analysis is shown to be consistent with 50 Ti scattering data.

Level structure of 106Ag

Abstract The level structure of 106 Ag has been investigated through the use of the 103 Rh(α, nγ), 105 Pd( 3 He, d), 107 Ag(p, d) and 104 Pd( 3 He, p) reactions. The charged particle reactions provided the energies of 47 levels ranging up to 1684 keV and l -values were determined from the angular distributions for the neutron and proton transfer reactions to most of the states. Fifty-two γ-rays were assigned as transitions between the levels resulting from the charged particle data. Through the use of a combination of the l -values and γ-ray transitions the members of the 1g 9 2 -2d 5 2 and 2p 1 2 -2d 5 2 configuration multiplets have been deduced. The 6 8.4 d isomeric state has been located at 88 keV. The measurement of Q -values for the charged particle reactions has permitted determination of the mass of 106 Ag with greater precision than previously.