Elastic scattering of light nuclei through a simple potential model

The phase function method is adapted to deal with the scattering on our proposed interactions for α–α and α–³He systems. The effect of the electromagnetic interaction is included in terms of a screened Coulomb potential. Based on our proposed potential models we present results for α–α and α–³He elastic scattering phase shifts which compare well with more detailed calculations.     

Elastic deuteron scattering on 12C and 16O nuclei in the alpha-cluster model

On the basis of the dispersive alpha-cluster model for target nuclei and the theory of multiple diffractive scattering, differential cross sections and analyzing powers for the elastic scattering of 400 and 700-MeV deuterons on ¹²C and ¹⁶O target nuclei were calculated in the pointlike-deuteron approximation. In these calculations, the amplitude for incident-deuteron scattering on nuclei was constructed with the aid of amplitudes for dα scattering that were obtained from a fit to data on d ¹⁶O scattering. The same features were calculated on the basis of the diffraction approximation with allowance for the internal deuteron structure by using the amplitudes obtained earlier for nucleon scattering on ¹²C and ¹⁶O nuclei within the same dispersive alpha-clustermodel. The latter made it possible to perform calculations without employing adjustable parameters. The observables calculated on the basis of either approach agree with available experimental data.     

Thermal neutron scattering parameters for light nuclei (A=12 to 27)

Neutron scattering lengths and free scattering cross sections were measured for isolated isotopes and natural elements in the mass region fromA=12 toA=27. By means of the Christiansen filter technique values for the coherent scattering lengths were obtained for the bound atoms of^12C,^13C,^14N,^15N,^16O,^17O,^18O, Mg and¹⁹F. Transmission experiments with neutrons of 0.51 meV, 1.26 eV and 5.19 eV yielded data for the free scattering cross sections of^19F,²³Na, Mg and¹⁹F. From all these results and with previous data the fundamental spin state scattering lengths for the concerned light nuclei have been deduced. The comparison of these values with resonance parameters has shown that the resonance data are complete. Therefore, values for the potential scattering radii could be obtained and discussed.     

Elastic and inelastic scattering of electrons by aligned light nuclei

The contribution to the elastic and inelastic scattering cross sections, , due to alignment of nuclei having axial symmetry was calculated for scattering of unpolarized, ultra-relativistic electrons by⁷Li atoms. This contribution turned out to be on the order of magnitude of the cross section ₀ previously calculated in the absence of nuclear alignment. For various nuclear orientations, the ratios /_o were calculated as a function of the momentum transfer q, which may be useful, for example, in increasing the reliability of identification of quantum numbers of nuclear states and multipole transitions.In contrast with the expression for _o, the expression for contains cross products of reduced matrix elements (RME), along with the squares of their moduli. This permits one, having previously experimentally found ₀ and under various kinematical conditions but for fixed q (the RME depend only on q), to obtain a system of equations for the RME and the statistical tensor g₂, which characterizes the degree of alignment of the nuclear target, along with the separation of the parallel and perpendicular cross sections as in the case of unaligned nuclei. Having solved the system of equations, one finds g₂ both in terms of the moduli of the RME of each multipole transition individually, and also in terms of their relative phases. The additional information thus obtained for each nuclear transition may serve as a more strict criterion for checking models of nuclei used in calculations than measurement of ₀ alone.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 94–98, January, 1990.     

Nuclear rainbow in the elastic scattering of <Superscript>16</Superscript>O nuclei on carbon isotopes

An investigation of refractive effects in heavy-ion scattering is continued. For the elastic scattering of ¹⁶O nuclei on a ¹³C target at E(¹⁶O) = 132 MeV, the differential cross sections are measured for the first time in addition to previous measurements for targets from the carbon isotopes ¹²C and ¹⁴C. Airy structures that are similar for all isotopes and which have close cross sections are observed and are found to be consistent with the energy systematics of Airy minima that were obtained previously. The volume integrals of the real and imaginary parts of the optical potentials found in the present study are nearly identical for all of the isotopes considered here and are also in good agreement with the systematics obtained previously.     

Alignment delays in the N = Z nuclei (72)Kr, (76)Sr, and (80)Zr

The ground state rotational bands of the N = Z nuclei (72)Kr, (76)Sr, and (80)Zr have been extended into the angular momentum region where rotation alignment of particles is normally expected. By measuring the moments of inertia of these bands we have observed a consistent increase in the rotational frequency required to start pair breaking, when compared to neighboring nuclei. (72)Kr shows the most marked effect. It has been widely suggested that these "delayed alignments" arise from np-pairing correlations. However, alignment frequencies are very sensitive to shape degrees of freedom and normal pairing, so the new experimental observations are still open to interpretation.     

Elastic scattering of α particles on light nuclei at Pα=7 GeV/c

Elastic scattering differential cross sections of α particles have been measured at P_α=7.0 GeV/c ($\text{T}\text{N}\text{=1.05}\text{GeV}$) on ¹H, ²H, ³He and ⁴He target up to a momentum transfer of ～4 (GeV/c)². A preliminary interpretation of the data is given in the framework of the Glauber theory.     

Elastic and inelastic scattering of polarized protons from even n=82 nuclei near isobaric analog resonances

Excitation curves for the elastic and the inelastic scattering of polarized protons on the target nuclei ¹³⁸Ba, ¹⁴⁰Ce, ¹⁴²Nd and ¹⁴⁴Sm have been measured in the energy region of prominent isobaric analog resonances. A detailed analysis of the data is presented. Definite J^π assignments are given for a number of parent analog states. Spectroscopic factors and amplitudes for configurations with the core in the ground state or in the 2₁⁺ excited state are derived from the elastic and inelastic proton decay amplitudes. They show consistency with sum rules including orthogonality conditions. Different methods for the-calculation of single particle decay widths have been applied. The qualitative agreement with present unified model calculations is remarkable; an overestimattion of the weak coupling structure, however, becomes apparent.     

Elastic and inelastic scattering of nucleons from 16O

Measurements of differential elastic and inelastic cross sections for neutron scattering from ¹⁶O at incident energies 18 to 26 MeV are presented. In addition to cross sections for neutron scattering differential cross sections for proton scattering up to 66 MeV are described in terms of phenomenological optical model potentials. At 24.5 MeV incident energy inelastic scattering up to 11.5 MeV excitation was measured. The elastic and inelastic compound nucleus contributions were examined. Direct inelastic scattering from the normal parity states was calculated using the DWBA and coupled-channel formalisms. The inelastic scattering cross section from non-normal parity state 2⁻ was calculated using the coupled-channel formalism via multi-step processes. Cross sections due to inelastic scattering from some of the states, which are thought to be members of an excited state rotational band were calculated using both vibrational and rotational approaches and were compared.     

Elastic scattering of 100 MeV protons and systematic optical model analysis

Using a Ge(Li) total energy detector the elastic scattering of 100 MeV protons from ⁵⁸Ni, ⁹⁰Zr, ¹²⁰Sn and ²⁰⁸Pb has been measured. Optical model fits with $\text{x}{}^2\text{N}$ of order unity have been made. The parameters of these fits varied systematically with A enabling the isospin dependence of the real part of the potential and its volume integral to be deduced. The limitations of the conventional optical model analysis in the case of ⁵⁸Ni are illustrated and discussed.     

Isovector giant resonances in light nuclei observed by (7Li, 7Be) reaction

Isovector giant resonances were studied with the (⁷Li, ⁷Be) reaction on ¹²C, ²⁴Mg, ²⁷Al, ²⁸Si and ⁴⁸Ti at an incident energy of 150 MeV. Differential cross sections were measured at forward scattering angles including 0°. We observed the octupole resonance at E_x ∽ 16 MeV and the giant dipole resonance at E_x ∽ 20 MeV in all residual nuclei.