A.I. Yavin

Scattering of antiprotons from carbon at 46.8 MeV

Abstract Antiproton-carbon elastic and inelastic scattering cross sections have been measured at 46.8 MeV over an angular range 6° ⩽ θ ⩽ 59° with a magnetic spectrometer. Fits to the elastic and inelastic 4.44 MeV excited state cross sections put realistic limits on the strengths of the real and imaginary parts of the antiproton-carbon optical potential. The continuum cross section due to carbon break-up appears to be smaller than it is for corresponding proton data.

Elastic scattering of antiprotons from Carbon Calcium and Lead at 180 MeV

Angular distributions for elastic scattering of 180 MeV antiprotons from 12C, 40Ca, and 208Pb have been measured over a wide angular range with a magnetic spectrometer. In general, microscopic calculations agree fairly well with the data. Optical-model fits with Woods-Saxon parametrization determine the magnitude and the relative strength of the real and imaginary potentials at the nuclear surface. When the shape of the potentials is derived from that of the charge distribution, the depth of the real potential is found to be shallow (30 MeV < V0 < 70 MeV). These results are in some disagreement with several models and predictions, but are consistent with the results of p-12C scattering at 46.8 MeV and with a recent a analysis of p-atom data.

Optical-model analysis of antiproton-nucleus elastic scattering at 50 and 180 MeV

Abstract Accurate antiproton-nucleus elastic scattering angular distributions measured at two incident energies,∼50 and ∼180 MeV, on 12 C, 40 Ca, 208 Pb and at 178.4 MeV on 16,18 O have been analysed in the framework of the optical model. Extensive searches on the relative sensitivities to the different potential parameters have been done. Optical potentials with charge-distribution geometries failed in reproducing the experimental data; the finite range of the interaction has to be taken into account. The corresponding optical potentials have shallow real parts 5 MeV ⩽ V 0 ⩽ 105 MeV, their imaginary depths are at least twice larger than their real depths. These features rule out some models but are consistent with an analysis of recent p -atom data. The sensitivity of the optical-model analysis of elastic scattering data to the details of the radial potential has been investigated. Target mass and energy evolution of the strong-absorption radius and reaction cross section confirm that the antiproton penetrates more inside the target nucleus when the incident energy increases. Some features of the phenomenological potentials are compared with the predictions of microscopic potentials.

Study of the (3He, d) reaction on even molybdenum isotopes

A study of single-particle proton strengths in odd-mass Tc isotopes was performed using the (3He, d) reaction. Angular distributions were measured from 8° to 70° and compared with calculations using the distorted-wave Born approximation. The l-values and spectroscopic factors were extracted and compared with (d, n) results. Proton configurations for the ground states of 92,94Mo and 96Mo were deduced from the analysis. Symmetry energies were extracted from the energy difference between the centroids of the T> and T< states. Various methods for DWBA calculations for unbound states are discussed.

The (n, p) reaction as a probe of Gamow-Teller strength

Abstract The ground state differential cross sections for the (n, p) reaction at 0° on 6 Li, 12 C and 13 C have been measured for 198 MeV neutrons with a precision of about 4% relative to the corresponding value for the H(n, p) reaction. These data, together with the accurately known ft values for the β- decay of 6 He, 12 B and 13 B provide three calibrations of the (n, p) reaction as a probe of Gamow-Teller strength for isospin raising transitions.

(3He, d) stripping to unbound analog states in Nb isotopes

Abstract The ( 3 He, d) reaction was studied on all stable Zr isotopes. Twenty-three unbound analog states in the Nb isotopes were populated. The observed cross sections were analyzed using two different methods for DWBA calculations of stripping to unbound analog states. The deduced proton spectroscopic factors are compared to the neutron spectroscopic factors obtained for the parent states from the (d, p) reaction studies. The agreement is generally good, except for the 97 Zr- 97 Nb isotope pair. The difference in the sensitivity to the transferred angular momentum between the (d, p) reaction and the ( 3 He, d) reaction to the analog states is discussed. The good agreement leads us to conclude that the ( 3 He, d) reaction to analog states may be used in nuclear spectroscopy for the study of levels in the parent states which are populated through large angular momentum transfer.

Gamow-Teller strength and giant resonances in 90Zr(n,p) at 198 MeV☆

Abstract The 90 Zr(n,p) 90 Y reaction has been studied at a bombarding energy of 198 MeV in a search of GT + strength. Up to 10 MeV excitation in 90 Y, we obtain a firm upper limit of S β + ⩽ 3.6. The majority of the strength at low excitations is identified as spin dipole.

Comparative study of the elastic scattering of 178.4 MeV antiprotons by the 16O and 18O isotopes

Abstract Elastic scattering of 178.4 MeV p has been measured on 16 O and 18 O isotopes. Both macroscopic and microscopic analyses of the data show differences which can be related to the neutron excess in 18 O

Inelastic scattering of antiprotons from 12C and 18O at 50 and 180 MeV

Abstract The angular distributions of the inelastic scattering of antiprotons for a few collective states of 12C and 18O have been measured. They exhibit a diffractive pattern, typical of strong absorption. Coupled channel analysis of these data has been carried out. The derived multipole moments agree fairly well with those obtained with other probes. Microscopic calculations performed in the framework of the DWIA formalism, using either the Paris or the Dover-Richard NN interaction are in good agreement with the data for the low-lying collective states. The present status of the experimental study of the unnatural parity levels is discussed.

Multi-purpose magnetic particle analyzer

Abstract A flexible magnetic particle analyzer is proposed. It will be used as (1) a broad range spectrograph; (2) a high intensity spectrometer; and (3) a high resolution spectrometer free of kinematic broadening effects.