F. Malaguti

Charge density and single-particle structure of 58Ni

Abstract The charge distribution of 58 Ni has been calculated by summing the squares of the proton wave functions in a one-body non-local potential whose parameters were adjusted to give the experimental centroid energies. The squared wave functions were weighted by the occupation numbers. A definite procedure to solve the problems connected with the state dependence of such a potential has been developed. The calculated 58 Ni charge density depends essentially on the ld state centroid energy and on the 1f 7 2 occupation number. These have been determined by a fit to the experimental charge density.

A diffusion model calculation of axial blocking dips of α-particles in aluminium

Abstract Angular blocking dips around the ⟨110⟩ axis in Al single-crystal of α-particles of about 2 MeV produced at a depth of 0.2 μm are calculated for the following values of the mean displacement v υ ⊥ τ of the decaying nucleus: v υ ⊥ τ = 0,4.4, 13, 30 pm. Calculations have been made on the basis of a continuum model with diffusion, where the effects of multiple scattering on the transverse energy distribution are taken into account by means of a diffusion equation as originally suggested by Lindhard. The results are compared with the blocking dips obtained through an extensive Monte Carlo calculation where the lattice atoms are allowed to vibrate. The agreement between the results of these two methods is very satisfactory. Significantly different results are obtained if the blocking dips are calculated according to the continuum (or halfway-plane) model without diffusion.

The systematics of nuclear single-particle states: (III). Widths and rearrangement energies

Abstract Widths and rearrangement energies are obtained from fragment distributions of single-particle states determined from one-nucleon pickup reactions on nuclei in the range 6 ≦ A ≦ 65. These show systematic features that are compared with the results of Brueckner-Hartree-Fock calculations.

The systematics of nuclear single-particle states (IV). The f72 shell

Abstract The centroid energies of particle and hole states in the 1 f 7 2 shell are combined to give the single-particle energies using the definition of Baranger, and are expressed as eigenvalues of a local Saxon-Woods potential. The variation of the occupation probabilities through the region where the shell is filling is determined. The asymmetry potentials for proton and neutron states are found to differ; they become equal by assuming a more rapid scaling than A 1 3 of the potential radius in a chain of isotopes.

Transverse energy distribution and the shape of blocking dips in real crystals

Abstract The calculated shapes of blocking dips differ from the experimental ones since models for charged particle motion with in crystals assume a perfect lattice. In this paper we suggest that the difference between the transverse energy distribution π(E⊥) of the particles coming out from a real crystal and that calculated in a statistical equilibrum continuum model, corrected for thermal vibration effects by a diffusion equation, accounts for crystal defects and is approximately independent of the distribution of transverse energy before diffusion and of the energy of blocked particles. The extraction of π(E⊥) from experimental dips requires the inversion of an integral equation, that is analy = tically solved in a particular case of practical interest. This would provide a way of analysing nuclear reaction time measurements that makes use of the full shape of the blocking dips. An illustrative example of the method to a blocking lifetime measurement in 27A1 (p,α) 24Mg resonance reactions is presented.

Crystal Blocking Measurements of the Time Delay of Fission Induced by {sup 32}S, {sup 48}Ti, and {sup 58}Ni Bombardment of W

The time delay in fission induced by bombardment of W with 180 MeV 32S, 240-255 MeV 48Ti, and 315-375 MeV 58Ni has been measured by observation of crystal blocking. There is a clear narrowing and a small increase in the minimum yield of the angular dips for fission compared with scaled dips for elastically scattered ions. This is interpreted as a fission delay of about 2 as, only weakly dependent on energy and atomic number. The delay is longer by 1 to 2 orders of magnitude than obtained from standard interpretations of measurements of prescission neutrons and giant-dipole-resonance gamma rays and from calculations of the nuclear dynamics in heavy-ion reactions.