S. Roman

Polarization in the elastic scattering of 12 MeV deuterons

Abstract Angular distributions are presented of the vector polarization of 12 MeV deuterons elastically scattered by Si, 52 Cr, 56 Fe, 58 Ni, 93 Nb, Ag and In. Large values of polarization were observed for Si, 52 Cr, 56 Fe and 58 Ni. The polarization diffraction pattern was seen to decrease systematically with Z up to silver but was found to increase for indium. The measurements were analysed in terms of an optical model which accounted for most of the results including those of Ag and In. Average sets of optical-model parameters have been found. The A and Z dependence of some parameters have been investigated.

Elastic and inelastic scattering of vector polarized deuterons by Fe and Ni isotopes

Abstract Vector analysing powers and cross sections for deuteron elastic and inelastic scattering by 54, 56, 58 Fe and 60 Ni were measured at a deuteron energy of 12.3 MeV. Large changes in the elastic scattering analysing power were observed for small changes in the target mass. The elastic data are well described by standard optical model calculations employing fixed real and spin-orbit geometry parameters. The analysis yielded a spin-orbit potential depth of about 6.5 MeV and a volume integral of the real central potential of about 365 MeV · fm 3 per nucleon for each nucleus. The variations of the measured analysing powers with the target nucleus are explicable in terms of a dependence of the strength of the imaginary potential upon the neutron excess ( N - Z )/ A . The data for the 2 + first-excited states are adequately described by a collective model analysis using both DWBA and coupled-channels formalisms. The coupled-channels treatment revealed a strong dependence of the predicted elastic and inelastic analysing powers on the mode of excitation and the magnitude of the deformation parameter.

Polarization of 17.8 MeV protons elastically scattered by nuclei

Abstract Angular distributions are presented for the polarization of 17.8 MeV protons elastically scattered by Be, S, Fe, Co, Cu, Zn, Ga, Ag and In at angles between 25° and 120° (lab). Targets of natural isotopic abundance were used and the experimental technique involved the single scattering of a totally polarized proton beam obtained by bombarding gaseous hydrogen with 40 MeV alpha particles. These results, together with the differential cross-section data and previous results for Si, Ca, 58 Ni 60 Ni and Mo, were analysed using an optical model automatic search programme. The geometrical parameters were fixed and systematic trends in the real central, imaginary central and spin-orbit potentials were investigated. Improved fits were obtained by reducing the radius of the spin-orbit potential with respect to the radius of the central potential.

Polarization of 17.8 MeV protons scattered by nuclei

Abstract Angular distributions are presented for the polarization of 17.8 MeV protons elastically scattered by C 12 , Si, Ca, Ni 58 , Ni 60 and Mo and inelastically scattered by C 12 and Ca 40 . An attempt has been made to fit the experimental results in terms of an optical model potential. To obtain information concerning the spin-orbit potential the remaining parameters were chosen consistent with values found for other energies and elements. The spin-orbit potentials required to fit the data were real with the exception of Ca where it was necessary to introduce an imaginary term in order to obtain a good fit. The variation in the depth of the real part of the central potential for the two Ni isotopes is described in terms of a symmetry potential of the form V 1 ( N − Z )/ A , with V 1 = 23±6 MeV. The experimental technique involved the single scattering of a totally polarized proton beam obtained by bombarding gaseous hydrogen with 40 MeV alpha particles.

The elastic scattering of 33 MeV polarized 3He particles by beryllium and carbon

Abstract Angular distributions of 3 He polarization in elastic scattering from 9 Be and 12 C, and in inelastic scattering to the 4.44 MeV state of 12 C were measured using a 33 MeV polarized 3 He beam. The polarization and cross-section data were successfully analysed in terms of the standard optical model. Selectively of the 3 He elastic polarization for various potential sets was established in both optical model and coupled-channel analyses. While it is possible to determine unambiguously the geometry of the spin-orbit term, its strength is strongly correlated with other optical model parameters.

Vector and tensor analysing power of (d, p) reactions and deuteron D-state effects

Abstract The vector and tensor analysing power was measured for (d, p) reactions on 9 Be, 12 C, 16 O, 19 F, 25 Mg, 28 Si and 40 Ca for lab reaction angles from 0° to 50° at 12.3 MeV incident deuteron energy. Fifteen transitions were studied including orbital angular momentum transfers l n = 0,1,2, 3. The experimental results were analysed in terms of distorted-wave theory including deuteron D-state effects. The calculations show that the deuteron D-state cannot be ignored in the description of the tensor analysing power. The j -dependence of D-state effects is discussed.

Stripping reactions and elastic scattering of 12 MeV vector polarized deuterons on 9Be and 12C

Abstract Angular distributions were obtained of the vector analysing power for 9 Be(d, d), 12 C(d, d), 9 Be(d, p) 10 Be and 12 C(d, p) 13 C reactions induced by 12 MeV polarized deuterons. Most features of the (d, p) reactions were adequately accounted for by DWBA calculations with optical-model deuteron potentials which described the elastic scattering at the same energy. The calculations distinctly favoured real central deuteron potentials around 100 MeV.

The j-dependence of (3He, d) and (3He, α) reaction analysing powers in the 1p shell

One of the most important experimental results from polarized deuteron studies is the ability to obtain reliable spectroscopic information from measurements of the vector analysin power in transfer reactions. With the availability of a polarized He beam it is of consid- erable interest to determine whether a similar j-dependence of the 3He analysing power exists. Cross section measurements in the 30 MeV region have shown that the (3He,d) and (3He,α) reactions can be quantitatively described by direct reaction theories. Therefore, j-dependence could provide a spectroscopic tool perhaps even more powerful than in reactions with polarized deuterons.

Elastic scattering of polarized 3He particles by16O and 40Ca

Abstract Angular distributions of analysing power and differential cross section have been measured for the elastic scattering of 33.3 MeV 3 He by 16 O and 40 Ca. The obtained results have been described in terms of the standard optical model with a spin-orbit potential characterized by a small diffuseness parameter of about 0.22 fm and strength around 3 MeV. The l -dependent optical-model potential has also been investigated.

Vector analysing power of the (d, p) reaction on 28Si, 52Cr and 88Sr AT 12 MeV

Abstract The vector analysing power of the (d, p) reaction leading to several states of the final nuclei 29 Si, 53 Cr and 89 Sr was measured using a 12.3 MeV vector polarized deuteron beam. The data exhibit a distinct j -dependence which is in accordance with known spin and parity assignments of the final states. Present experimental results are compared with existing measurements of proton polarization. An extensive DWBA analysis confirms an applicability of the method for calculating the vector analysing power for most reactions involving orbital momentum transfer l = 1, 2, 3. It is less satisfactory in cases with l = 0. The effects of optical model parameters and particularly the spin-orbit distortion in the deuteron and proton channel are discussed.