Th.A.J. Maris

High energy (p,2p) reactions and proton binding energies

The energy carried away by each of the two coincident protons from (p, 2p) reactions in elements bombarded by 185 MeV protons has been measured by range analysis. To the extent that the collision is quasi-elastic, the difference between the sum of these energies and the incident energy, corrected for the recoil energy of the residual nucleus, gives the binding energy of the struck proton in the nucleus. Sharp groups which can be associated with the nuclear shell structure have been observed in the light elements. The results determine directly the spin-orbit splitting in the 1p-shell and the binding energy of the 1s-shell for the lightest nuclei. Only the spectrum of Be9 might give some indication of an α-particle structure.

Quasi-elastic scattering and nuclear structure

Abstract Energy and angular correlation measurements on the two protons emerging from high energy (p, 2p) processes may give direct information on the structure of the ground state of the bombarded nucleus and of certain excited states of the residual one. Expectations are derived on the basis of the assumptions of the approximative validity of the shell model and the Serber-Chew hypothesis of the reaction mechanism. The influence of multiple collisions in the nucleus is considered.

Quasi-free electron-proton scattering (II)☆

Abstract It is shown that, from angular and energy correlation measurements on electron-proton pairs emerging from the scattering of high energy (300–1000 MeV) electrons on nuclei, detailed information on the energy levels and structures of the upper and lower shells of light and medium nuclei could be obtained. A calculation in which the distortion of the outgoing proton wave is taken into account has been performed for C12. As compared to the result for zero distortion, the absolute magnitude of the correlation cross section is reduced, but the shape of its angular distribution is practically unchanged. Consequently the observed energy and angular correlations would immediately give both the binding energy and the momentum distribution of the nuclear proton in the shell model state out of which it has been ejected. From an extrapolation to other nuclei of the calculated value of the reduction factor for the cross section, it is expected that this situation prevails at least up to nuclei with A = 50. Finally some corrections are qualitatively discussed.

Inelastic scattering of 185 MeV protons on oxygen, calcium and carbon

Abstract The energy spectra at various angles for the inelastic scattering of protons near 180 MeV on oxygen, calcium and carbon have been measured with a magnetic analyser. Maxima corresponding to excited states of the target nuclei have been resolved and some differential and total cross sections are reported.

Studies of inelastic scattering of 185 MeV protons on carbon

Abstract Studies of the inelastic scattering of 185 MeV protons on carbon have been performed using a magnetic analyser. Differential cross sections of protons, exciting clearly resolved levels in C12, are given.

Inner shell structure of nuclei

States in which the inner shells are intact are comparable with atomic states leading to optical transitions. The nuclear states corresponding to x-ray states in atoms have holes in inner shells. The purpose of this note is to report preliminary results of a method of investigating such states. (A. C.)

Some remarks concerning measurements on inelastic scattering of 155–185 MeV protons on carbon, oxygen and calcium

Abstract Semi-quantitative theoretical expectations for the differential cross sections of high energy inelastic proton scattering are summarized and compared with the experimental results for carbon, oxygen and calcium. The general agreement is satisfactory. High energy proton scattering at small angles seems a promising tool for the study of the giant gamma resonances at least in light nuclei. Some remarks concerning the measured asymmetries and polarizations of the inelastically scattered protons are made.

Quasi-free diffraction scattering

Abstract It is shown that a certain type of non-coplanar quasi-free proton-proton scattering on heavy and medium nuclei is able to give direct and clear information on the structure of the target nucleus and the mechanism of the interaction. It is expected that the parities and orbital angular momenta of the occupied single particle states in the least bound shell, and for some cases in the stronger bound shells, can be determined. In addition the radial extension of the surface interaction zone and its distance from the centre of the nucleus would follow immediately from the expected interference patterns.

Inelastic scattering of 185 MeV protons on nuclei with masses from fluorine to potassium

Abstract Inelastic spectra of 185 MeV protons scattered at two different angles on nuclei from fluorine to potassium are reported.

Inelastic high energy nucleon scattering on light nuclei

Abstract The excitation of a nucleus bombarded by nucleons of a few hundreds of MeV is considered as the result of individual interactions of the incoming nucleon with the nucleons of the nucleus. A simple two-particle model, in which a bombarding particle excites a particle moving in a potential well, has been calculated in the first Born approximation. It is shown that the resulting angular distributions have a strong forward dip and vanish at large angles. To a certain extent this result still holds for the case of a nucleus consisting of Fermi- particles with common and isobaric spins. In first order only those states can be excited whose wave functions have, in the sense of the independent particle model, a component differing only in the state of one particle from the ground state wave function. In the case of neutron scattering the cross section has a forward dip if the space part of the wave function of the excited particle is orthogonal to the space part of its ground state wave function. If this is not so, for example if the excitation can occur by a pure spin exchange, there may be a forward maximum. In proton scattering the Coulomb interaction could result in a forward peaked angular distribution by didipole excitation as well as in the above mentioned case of monopole transition. In higher approximation two or more particles in the nucleus can be simultaneously excited. The resulting cross sections are expected to be smaller and more isotropic than in the case of a one-particle excitation. The angular distributions for two types of collective excitation have also been calculated, in the first Born approximation, namely for the lowest quadrupole surface vibration and for the dipole vibration of the nuclear charge. The qualitative features of the experimentally measured cross sections of the scattering of 185 MeV protons on C12 are shown to be in agreement with the theoretical expectations.