(3HE,ALPHA) REACTIONS ON CHROMIUM ISOTOPES

The reactions 50,52,53,54Cr(3He, α)49,51,52,53Cr have been studied at an incident energy of 18 MeV using a broad-range magnetic spectrograph as well as solid state detectors. Angular distributions were obtained for all isotopes. The relative isotopic cross sections were accurately determined by measurements with a target of mixed Cr isotopes. Coulomb energy displacements are obtained from the observation of f 7 2, d 3 2 and s 1 2 analogue states at excitation energies between 5 and 13 MeV. The spectroscopic factors from a DWBA analysis give information about the neutron configurations in the Cr isotopes which are discussed in the particle-hole excitation picture and in terms of the unified model. Centres of gravity for the f 7 2, d 3 2, and s 1 2 orbits are determined. The spectroscopic factors of the analogue states are obtained from solutions of the Lane equations for the bound states using a surface-type isospin potential. In a simplified analysis, the effects of the surface potential are simulated by varying the bound-state radii, keeping the depth of the potential constant for the ifT < and T> states. These procedures yield similar results, which are in agreement with the sum-rule predictions. The resulting radii suggest that the inner nucleons occupy a volume smaller than that corresponding to a potential radius R = 1.25 A 1 3. © 1969.