A. Uguzzoni

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 neutron-neutron scattering length from reactions with tritium targets

Abstract The 3 H(n, d)2n reaction was studied at 15.1 MeV neutron energy. The deuteron energy spectrum at 0° is well reproduced by using the Watson approximation with a n−n = −17 fm. A satisfactory agreement has been found among the a n−n values derived, by the same procedure, from all but one published work with tritium targets and two neutrons in the final state.

The use of a checker board counter in blocking experiments

The use of a checker board counter to obtain angular distribution of charged particles around crystallographic directions is described. Various experimental possibilities are discussed. Blocking patterns obtained with a Si single crystal are reported.

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.