Lw Put

The form factor of the real part of the α-nucleus potential studied over a wide energy range

Abstract Differential cross sections for elastic scattering of α-particles from 90Zr and 92Zr were measured over a wide angular range at a number of energies between 40 and 120 MeV. Excitation functions for scattering from 90Zr were measured at three angles over the range 28–54 MeV. The data were analyzed in terms of the optical model. Apart from the standard Woods-Saxon form factor, a number of other parameterizations of the real potential form factor were used. The very best fits to the data were obtained in a model-independent analysis in which the real potential was represented by a spline function. Folding model potentials were also employed. The data for E α ≧ 80 MeV can be very well accounted for by an optical potential with constant form factors and real and imaginary well depths which vary smoothly with energy. At lower energies, however, the data can only be fitted in detail if for the real potential a form factor is used which is different from the one used at high energies. Attempts to explain the energy dependence of the form factor, e.g. in terms of effects which are neglected in the regular optical model description, are discussed. No satisfactory explanation has been obtained. The investigation of the uniqueness of the determination of the real potential revealed that at high energies as well as at low energies the elastic scattering is sensitive to the shape of the real potential over the range 4 to 9 fm, and very insensitive to the deep interior part and the tail of the potential.

The 116Sn(d, t)115Sn reaction and the investigation of deeply bound hole states in the odd-A tin isotopes

Abstract Single-neutron pick-up via the (d, t) reaction was studied at E d = 50 MeV on all stable, even- A tin isotopes with an emphasis on the pick-up from the first major shell below the valence shell. The deeply bound hole states thus observed exhibit themselves as a gross structure phenomenon with a systematic variation of its width as a function of neutron number. The most extensive study was done for the 116 Sn(d, t) 115 Sn reaction for which angular distributions were obtained not only for the deeply bound hole states but also for the pick-up of valence nucleons, and for the excitation of the isobaric analogue states. A DWBA analysis yielded the full sum-rule strength for the pick-up of the valence nucleons. It located in the gross structure about 45% of the combined 1g 9 2 , 2p 1 2 , 2p 3 2 and 1f 5 2 strength. Additional strength may be found in the continuous “background” on which the gross structure peaks are riding. A systematic study of the gross structure shapes and cross sections in all odd- A tin isotopes is presented. The observed variation in the spreading of the 1g 9 2 hole strength as a function of neutron number is compared with recent calculations.

Unusually strong excitation of the 1.59 MeV 0+ state in the 100Mo(d,6Li)96Zr reaction

In a study of the 94,96,98,100Mo(d, 6Li)90,92,94,96Zr reactions at Ed = 45 MeV an unusually strong excitation of the 1.59 MeV 0+ state in 96Zr is observed. The variation in the 0+ strength from one zirconium isotope to the other can be qualitatively accounted for by the changing proton configuration with neutron number.

Proton-hole states in 115In observed in the 116Sn(d, 3He) reaction

Abstract The 116 Sn(d, 3 He) 115 In reaction has been investigated at E d = 50 MeV. Thirteen transitions to states up to 3 MeV excitation energy were studied. The measured angular distributions were compared with DWBA calculations and transferred angular momenta and spectroscopic factors were deduced. Levels at 1.04, 2.23 and 2.52 MeV were found to be excited most likely by l = 3 angular momentum transfer in contrast to previous investigations at lower incident energies in which no l = 3 transitions have been observed.

The supersymmetry scheme and E2 transition rates in the Pt region

Elastic and inelastic proton scattering from 191Ir, 193Ir and 194Pt have been studied at Ep = 50 MeV. The E2 reduced transition rates obtained for the low-lying states in these nuclei agree qualitatively with the predictions of the supersymmetry scheme recently proposed for these nuclei.

Four-nucleon pickup from 64Zn and 64Ni

The 64Zn and 64Ni(d, 6Li) reactions have been studied at 55 MeV bombarding energy. Eight final states in 60Ni and eight in 60Fe were identified and angular distributions were measured for these transitions from 8° to 35° in the lab system. A zero range, cluster model DWBA analysis is presented and several L-assignments are made. The L = 0 transitions both from the present work and from (6Li, d) data in the literature, are discussed in terms of the isovector pairing model. A brief comparison of the 64Zn(d, 6Li) results with previous (6Li, d), (t, p) and (p, t) data leading to 60Ni is also presented.

Investigation of proton hole states in 109, 111Ag excited in the 110, 112Cd(d, 3He) reaction

Abstract The 110, 112Cd(d, 3He)109, 111Ag reactions have been investigated at Ed = 50 MeV. Twelve transitions to states in 109Ag and twelve to states in 111Ag were studied. The measured angular distributions were compared with DWBA calculations and lp transfers and spectroscopic factors were deduced. In both 109Ag and 111Ag a possible low-lying 9 2 + state is found that has not been reported previously. Admixtures of 2p 3 2 shell components are found to be important in low-lying negative parity states. The results are compared with calculations in the Alaga model and the weak coupling model.

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.

Study of even-A zirconium and strontium isotopes with the (d, 6Li) reaction

Abstract All stable even-A molybdenum isotopes and 90, 92 Zr have been investigated with the (d, 6 Li) reaction at E d = 45 MeV to study proton- and neutron-pair correlations. Differential cross sections were measured for states up to E x = 3 MeV in 86 Sr, 88, 92, 94, 96 Sr and up to 6 MeV in 88 Sr and 90 Zr. Particular attention was paid to the comparison of α-pickup data with two-nucleon pickup data. The population of low-lying 0 + and 5 − states for two-neutron and four-nucleon pickup reactions was calculated using simple phenomenological wave functions for the initial and final states. The results of these calculations are in satisfactory agreement with the data.

Scattering of 30 MeV protons from 28Si, 58Ni and 120Sn at large backward angles

Abstract With the recently completed AVF cyclotron of the University of Groningen, existing data for 30 MeV proton scattering from 28 Si, 58 Ni and 120 Sn have been extended to scattering angles up to 178°. An enhanced backward scattering, which might be expected because of exchange effects, is not observed.