K. Hosono

Projectile break-up and the continuum spectra of the (3He, d) reaction

Abstract Deuteron continuum spectra induced by 70,90 and 110 MeV 3He particles have been measured for a number of target nuclei. Each spectrum shows a broad bump at forward angles, the peak energy of which is about 2 3 of the incident 3He energy and the cross section is nearly proportional to the radius of the target nucleus. The results are compared with projectile break-up calculations reflecting the internal deuteron momentum distribution in 3He. The good fit of the calculations shows that the continuum bump originates mainly from the projectile break-up process, and the mass number dependence of the cross section indicates that such a break-up reaction occurs at the peripheral region of the target nucleus.

Optical model and folding model potentials for elastic scattering of 56 MeV polarized deuterons

Abstract Differential cross sections σ and all four analyzing powers Ay, Axx, Ayy and Axz have been measured for deuteron elastic scattering from 12C, 16O, 40Ca, 58Ni, 90Zr, 118Sn, 144Sm and 208Pb at 56 MeV. The tensor analyzing power Axz was measured using horizontally polarized deuterons. These data were analyzed in terms of an optical potential containing central, spin-orbit and TR type tensor terms. A complex TR tensor potential was necessary to explain Axz and the quantity X 2 = (2A xx + A yy ) √3 . The optical potentials obtained were compared with exact folding model calculations. The real part of the TR tensor potential is generally smaller than the folding model potential, especially for heavier nuclei. The imaginary TR potential is comparable with the folding model for lighter nuclei and is smaller than the folding model for heavier nuclei. The folding model TR potential overestimates the amplitudes of the Axz and X2 data. Features of the σ, Ay and Ayy data at large angles are discussed in connection with nuclear rainbow scattering.

Proton-neutron correlation in the deuteron breakup at 56 MeV and prior-form DWBA analysis

Abstract Proton-neutron angular correlations in the 12 C, 51 V and 118 Sn(d, pn) reactions have been measured at 56 MeV to investigate the deuteron breakup process. The elastic breakup which leaves the target nucleus in its ground state dominates the coincident spectra. The elastic breakup cross sections are estimated to be 36–48% of the inclusive breakup yields at 15° or 17.5°. In the angular correlations the protons are emitted predominantly on the side of the beam opposite to the neutrons. The experimental data have been analyzed using the prior-form DWBA. For both nuclear and Coulomb breakup, sufficient convergence of the calculations is obtained by including the pn angular momenta up to l = 2. For the nuclear breakup calculations, the l = 0 and 2 contributions dominate the cross sections. For the Coulomb breakup the l = 1 contribution is predominant. In the calculations the effect of the Coulomb breakup is seen at forward angles of the angular correlation. The DWBA calculations reproduce fairly well the coincident energy spectra and the angular correlations in the angular region where the protons are emitted on the side of the beam opposite to the neutrons. On the other hand the calculations overestimate the break-up cross sections by a factor of 2 to 10 in the angular region where the protons are emitted on the same side of the beam as the neutrons. The distributions of deuteron c.m. angular momenta that contribute to the breakup amplitude are examined to obtain information on the region of space in which the breakup reactions takes place.

Angular correlation of (3He, pd) reactions at 90 MeV and elastic break-up of 3He particles

Abstract Proton-deuteron angular correlations in the 12 C, 51 V, 90 Zr( 3 He, pd) reactions have been measured at 90 MeV to investigate the break-up process of the 3 He particle. The p-d pairs originate mainly from the break-up of the 3 He without target excitation (elastic break-up). In the coincident deuteron spectra, peaks at forward angles are observed at energies corresponding to the minimum recoil energy of the target nucleus. The p-d angular correlations show oscillatory patterns at large angles. The experimental results of the elastic break-up have been compared with the calculations of the radial-cutoff plane-wave Born approximation. By adjusting the cutoff radius, characteristic features of the experimental results are reproduced by the calculations, except for the absolute cross section. The results suggest that the elastic break-up process is associated with the diffractive scattering of the center of mass of the 3 He particle. The elastic break-up contribution to the break-up yields of the inclusive ( 3 He, d) reactions is also discussed.

Analyzing powers of the continuum spectra: 65 MeV polarized protons on 12C, 28Si, 45Sc, 58Ni, 93Nb, 165Ho, 166Er and 209Bi

Abstract Analyzing powers of the continuum spectra were measured for 65 MeV protons from 12C, 28Si, 45Sc, 58Ni, 93Nb, 165Ho, 166Er, 209 Bi ( p , p# prime; X ) and ( p , dX) reactions and from 93Nb, 209Bi( p , αX) reactions. The analyzing powers of the continuum spectra were found to be small at forward angles where the pre-equilibrium process is important. However they do not show a systematic tendency. This feature indicates the importance of the spin-dependent interaction as well as nuclear structure effects. On the other hand, the analyzing powers were very large and positive at backward angles where the shape of the energy spectra resembles that of an evaporation spectrum. The maximum values of the analyzing power in the backward hemisphere depend on the target mass for the A 93 Nb ( p , p ′ X ) , ( p , dX), ( p , αX) reactions at EX = 20 MeV, respectively. These large values are mainly due to the entrance channel effect. There is no appreciable even-odd mass effect on the analyzing power for medium-mass nuclei. These features were unexpected from the conventional pre-equilibrium reaction models.

Polarization transfer observables for proton inelastic scattering from 12C at 0

Abstract Polarization transfer (PT) observables in the 12 C (p,p′) reaction at 0° for 392 MeV protons have been measured. The excitation strengths are decomposed into the spin-flip part and the non-spin-flip part by using the obtained PT observables. The PT observables for excitation of the 1+, T=0 and 1+, T=1 states are compared with distorted wave impulse approximation calculations. The strength ratios of the isoscalar spin-dependent term to the isovector tensor term and the isovector tensor term to the isovector spin-dependent term are reasonably consistent with the Franey and Love interaction.

Measurements of analyzing powers Ay, Axx, Ayy and Axz in dp elastic scattering at Ed = 56 MeV

Abstract The differential cross section and all components of the analyzing powers A y , A xx , A yy and A xz have been measured in dp elastic scattering at 56 MeV. This is the first measurement of A xz in the cyclotron energy region. A xz has been measured with the beam polarized in the horizontal plane using the polarization tagging method. Faddeev calculations have been performed for four cases of the NN interaction. The Coulomb correction gave smaller effects at the present energy than at lower energies. Three of them reproduce the experimental data well. The agreement between the calculations and data for A xz was better than that reported at lower energy. The deuteron asymptotic D- to S-state ratio has been obtained and is consistent within the limits of uncertainty with previously obtained values.

Systematic study of the (d, p) reaction with 56 MeV polarized deuterons

Abstract Differential cross sections and vector analyzing powers were measured for the (d, p) reaction with 56 MeV polarized deuterons. The investigation covered the transitions to the single-particle states of the 1p. 2s, 1d. 2p, 1f, 3s, 2d and 1g shells. The analyzing powers showed a j -dependence which depended on the number of nodes in the radial wave function of the transferred neutron. DWBA and adiabatic model calculations were carried out. The DWBA calculations reproduced the experimental cross sections and analyzing powers for the stripping to the j > states. The adiabatic model did not necessarily improve the fits to the data for these transitions. As for the j transitions, on the other hand, the DWBA calculations could not reproduce the experimental angular distributions, while the adiabatic model calculations improved the agreement with the experimental data.

Study of 112Cd via high-resolution (d, d′) and (p, p′) reactions and IBA model calculations

Abstract High-resolution inelastic-scattering measurements on 112 Cd with polarized deuterons (20 MeV) and polarized protons (16 and 65 MeV) provide complete spectroscopic information. Transition moments are obtained from the angular distributions of the cross section and analyzing power in a coupled-channel reaction analysis. The results are compared with interacting boson model predictions aiming to describe intruder states, quadrupole-hexadecapole and quadrupole-octupole excitations.

DWBA analysis of (3He, d) reactions at 90MeV and contributions from the nuclear interior

Abstract 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.