Search

Differential cross sections of 3He elastic scatterings and (3He, d) reactions have been measured at 90 MeV for 28Si, 54Fe, 58Ni, 90Zr and 124Sn. From the optical-model analysis of the elastic scattering, both shallow ( V ⋍ 105 MeV ) and deep ( V ⋍ 150 MeV ) potentials of 3He were obtained. The shallow potentials correspond to the ones which were determined uniquely from other measurements extended to more backward angles. The (3He, d) reactions have been analyzed with the DWBA using the shallow and deep potentials for 3He. The calculations using the deep potentials reproduced the data well, but those using the shallow ones did not. The contributions from the nuclear interior were investigated through the radial cutoff in the DWBA. The calculations using the shallow potentials reproduced the data well when the radial cutoffs were introduced. The effects of the radial cutoff were very small when the deep potentials were used. It was found that a much greater reduction of the contributions from the nuclear interior was needed when the shallow potentials were used in the DWBA calculations.

The double-differential cross section d2σ/dΩ dE, analyzing power Aγ, polarization Py' and polarization transfer coefficient Ky'y were measured for the ( d , p X ) reaction with 65 MeV deuterons for 12C at 14.0° and for 58Ni at 7.0°, 14.0°, 20.5° and 40.0°. The experimental data were analyzed within the framework of the post-form DWBA appropriate for the “spectator breakup”, and the preequilibrium exciton model together with the evaporation mode. The experimental angular distributions are well explained by taking account for these processes over the whole proton energy region observed.

Proton continuum spectra induced by 56 MeV deuterons have been measured for 14 elements ranging from 12C to 209Bi. Each spectrum shows a prominent bump at forward angles due to the break-up of the incident deuteron. The peak energy of the bump is about half the deuteron energy for light elements and increases slightly for heavier elements. Projectile break-up calculations reproduce well the spectral shapes and the angular dependence of the bump spectra. The characteristics of the bump spectra are determined by the proton momentum distribution in the deuteron. The break-up cross section increases with target mass and is nearly proportional to ( A 1 3 + 0.8) 2 . The target mass dependence indicates that all partial waves smaller than the grazing angular momentum contribute to the deuteron break-up cross section at this energy. The total break-up cross section amounts to 24–35% of the deuteron total reaction cross section.

Inelastic scattering exciting the ${2}^{+}$ and ${4}^{+}$ members of the ${K}^{\ensuremath{\pi}}$${=2}^{+}$ \ensuremath{\gamma}-vibrational band in $^{152}$,154Sm, $^{160}\mathrm{Gd}$, $^{164}\mathrm{Dy}$, $^{166}$,168Er, $^{176}\mathrm{Yb}$, $^{182}$,184W, and $^{192}\mathrm{Os}$ has been measured with 65-MeV polarized protons. Coupled-channel analyses have been performed assuming the \ensuremath{\gamma}-vibrational model or the asymmetric rotor model. A large hexadecapole (${Y}_{42}$) term in the \ensuremath{\gamma} motion is necessary in both models in order to reproduce the experimental data. The quadrupole (${Y}_{22}$) and hexadecapole (${Y}_{42}$) transition strengths to the \ensuremath{\gamma}-vibrational band have been extracted systematically from the optical potential parameters and the deformation parameters for the first time. These show a strong mass number dependence, and can be understood qualitatively by a simple geometrical picture together with the quadrupole (${Y}_{20}$) and hexadecapole (${Y}_{40}$) moments. The experimental ${Y}_{22}$ and ${Y}_{42}$ strengths have been compared with a random-phase-approximation calculation. This suggests the importance of the hexadecapole degree of freedom in the \ensuremath{\gamma} vibration. A density-dependent Hartree-Fock calculation explains the quadrupole (${Y}_{20}$) moments and the trend of the hexadecapole (${Y}_{40}$) moments of the deformed optical potentials very well. The effect of the density dependence of the effective interaction is also discussed through the ${Y}_{20}$ moments and ${Y}_{22}$ strengths.

The 28 Si ( 3 He, d) 29 P reaction has been studied at an incident energy of 29.3 MeV. Comparisons of DWBA and CCBA analyses of angular distributions for low-lying bound states show that channel-coupling effect is not important except for stripping to the 1.95-MeV 5/2 + state. Angular distributions for resonance states are analyzed by using Gamow functions as form factors for DWBA calulations. Such a description gives a reasonable account of the experimental angular distributions except that it fails to reproduce experimentally observed j -dependence.

Low-lying states in 83 Se have been studied through proton-induced isobaric analog resonance (IAR) reactions. Excitation functions for elastic and inelastic proton scattering were measured in the bombarding energy range 4.5– to 7.7 MeV. Angular distributions of proton inelastic scattering cross sections for the reaction 82 Se(p, p') 82 Se(0.655 MeV 2 + ) and angular correlations of the inelastic protons and the associated 2 + -0 + de-excitation γ-rays were measured on observed resonance peaks. In the analysis for the inelastic scattering, direct reaction contributions to the IAR were taken into account. Correlations between the low-lying states in 83 Se and the excited 2 + core state are discussed.

The elastic scattering of polarized protons from 16 nuclides in the f-p shell region was measured at a bombarding energy of 65 MeV. A conventional optical model analysis has been performed thoroughly and good fits have been achieved. The asymmetry term in the optical potential was deduced. We found that the volume integral of the asymmetry term depends on the mass number, in contrast with the A-independence claimed in previous works. The depth of the term is about zero when A = 40 , increases gradually with the increasing A, and amounts to 20 MeV at A -= 60.

Inelastic scattering exciting the 22+ and 42+ members of the γ-vibrational band in 168Er has been investigated with 65 MeV polarized protons. A coupled-channel analysis has been performed assuming both the γ-vibrational model and the asymmetric-rotor model. A large hexadecapole term (Y42 + Y4−2) in the γ-motion is necessary in order to reproduce the experimental data.

Angular distributions of elastic and inelastic scatterings on 28,29,30 Si were measured with a 51.9 MeV proton beam. The blocking effect in the core-excitation of 29 Si due to the antisymmetrization between the excited-core and the extra neutron was investigated. Optical model and distorted wave Born approximation analyses were performed using a macroscopic form factor for a collective excitation of 28,29,30 Si and a microscopic form factor for a single particle excitation of 29 Si. In the case of 29 Si, a mixing of an excited-core state and a single particle state was taken into account following the intermediate-coupling model calculation. Deformation parameters β 2 of 28,29,30 Si were extracted to be 0.42, 0.36 and 0.36, respectively. The reduction in the deformation parameter of 29 Si is considered to manifest the blocking effect of 25±14% in the core-excitation.

Cross sections and tensor analyzing powers, A xx and A yy of the continuum spectra in 58 Ni and 90 Zr( d , pX) reactions were measured at 56 MeV in the angular range between 6° and 30°. A prominent bump due to deuteron breakup was observed in the proton spectra. The peak energy of the bump is about one half of the incident deuteron energy. Tensor analyzing powers of magnitude 0.1–0.2 were observed at the high-energy side of the breakup spectra. The cross section and tensor analyzing powers were calculated based on a projectile breakup model using the S- and D-state momentum distributions of the deuteron derived from the Reid soft-core wave functions. In the calculation the tensor analyzing powers originate from the deuteron D-state alone. The experimental data at forward angles were roughly explained by the calculations except for the low-energy end of the spectra. The observed tensor analyzing powers at forward angles seem to reflect the effect of the deuteron D-state.

The measurements were made at angles of the center of mass extending from 14° to 128° or 172°. The yield of inelastic scattering at most angles was of the same order in the elastic scattering. A Thomas type spin-orbit coupling of the optical potential is useful for the elastic scattering at backward angles. Discrete and continuous ambiguities in the optical model parameters appeared in the analysis. The experimental values of inelastic scattering were predicted fairly well by the DWBA theory, and the deformation parameters β 2 were about 0.5. In the coupled channel analysis, the predicted values of elastic scattering were much different from the results of optical model analyses by coupling to the inelastic channel, and the potential whose imaginary part was shallower than that given by the optical model analysis gave better fit. The value of β must be -0.5 for 39.6 and 34.7 MeV.

A brief description on the Kyoto University tandem upgrading project is presented. The project consists of replacing the old 5 MV tandem Van de Graaff by an 8UDH pelletron. The old pressure vessel and beam lines are used again without significant modification. The project is planned to be completed at the end of 1989.

Elastic scattering of 65 MeV polarized protons from Sm isotopes, $^{164}\mathrm{Dy}$, and $^{172}\mathrm{Yb}$ has been measured. The volume integrals of the real central part and the spin-orbit part of the optical potential show anomalously low values for deformed nuclei. The origins of these anomalies are discussed.NUCLEAR REACTIONS $^{144}\mathrm{Sm}$, $^{148}\mathrm{Sm}$, $^{150}\mathrm{Sm}$, $^{152}\mathrm{Sm}$, $^{154}\mathrm{Sm}$, $^{164}\mathrm{Dy}$, $^{172}\mathrm{Yb}$(p,p), $^{164}\mathrm{Dy}$(p,p\ensuremath{'}), $E=65$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta})$, $A(\ensuremath{\theta})$; deduced optical-model parameters, coupled channel parameters, volume integrals for the real central potential, volume integrals for the real spin-orbit potential.

Elastic scattering of polarized protons from sd and fp shell nuclei has been studied with high-purity germanium detectors. The mean square radius of the central real part of the fitted optical potential was found to be of the form a + bA 2 3 . Comparison with the radius from electron scattering gives the range of the effective two-body interaction and its A dependence as 〈 r 2 〉 d =(4.5±0.4)+(0.16±0.03) A 2 3 fm 2 .