Search

A coincidence experiment was performed on the24Mg(16O,12Cα) reaction at an incident energy of 84.6 MeV. The measured relative energy spectra show the excitation of16O selected states decaying into the α-12C channel.

A level atEx=14.467 MeV in20Ne has been found to have some quartet component, possibly of [211] configuration. By using the value ofVp,sd recalculated on the basis of the results of Middleton, Garret and Fortune on the12C(12C, α)20Ne reaction and the value ofVsd,pf taken from the work of Arima, Gillet and Ginocchio, the unknown value ofVp,pf would result of the order of 200 keV. This seems to confirm the hypothesis of the independence of the quartet interactions from the number of excited quartets.

Differential cross-sections for the elastic scattering of protons by12C have been measured at energies between 1.5 and 4.0 MeV, in steps of 0.5 MeV, in order to search for a possible cluster structure in light nuclei. The experimental results have been compared with the predictions of the optical model, which fit the general trend of the data. Some discrepancies at small angles have been found. The presence of correlations between the cross-sections of the4He(p, p) reaction and a suitable function of the elastic-scattering cross-sections for protons on12C has been investigated. The results of this analysis seem to confirm that the structures in the experimental cross-sections (not accounted for by the optical model) are correlated to the behaviour of the4He(p, p) cross-sections at the same energies.

The possible presence of molecular structures in the21Ne composite system has been investigated by means of9Be+12C elastic scattering in the energy rangeEc.m.=(6.23÷12.06) MeV at θc.m.=127.7°. The SDM analysis of the excitation function has pointed out the existence of intermediate-width statistical fluctuations of molecular nature together with compound-nucleus fluctuations. The intermediate coherence energies of about 300 keV correspond to a mean lifetime τ≈2.2·10−21 s for the overlapping molecular states.

An extension of the spectral-density method is presented which, in some cases, allows a model-independent evaluation of the relative pre-equilibrium contribution to the experimental cross-section. Moreover, the method allows the independent extraction of the energy coherence widths and of the corresponding weights for the statistical mechanisms contributing to the reaction. The results relative to the27Al(3He,p)29Si reaction are reported.

The effect of mixed reactions on the statistical Ericson's cross-section fluctuation theory is considered to explain the experimental evidence of a significative cross-correlation between excitation functions of the fragments emitted in dissipative heavy-ion reactions. The applicability of the usual statistical methods to determine coherence energies is analysed.

The reactions32S(τ, d)33Cl and32–33S(τ, α)31–32S have been studied at 10.4 MeV incident energy. Absolute differential cross-sections have been measured and angular distributions have been analysed in terms of the distorted-wave Born approximation. Good agreement is obtained between experimentalS-factors from the reactions on32S and the results of recent theoretical calculations, whileS-factors from the33S(τ, α)32S reaction are found to be considerably larger. The use of the (τ, α) reactions to obtain spectroscopic information and its DWBA analysis are examined and the accuracy of the extractedS-factors discussed.

The reaction10B(d, p)11B has been investigated in the deuteron energy range from 1 to 2 MeV. The angular distributions have been analysed in terms of direct mechanism and compound-nucleus formation. A parameter-independent evaluation of the reduction factor is given. Even at these low energies, the spectroscopic factors obtained for the levels in11B by means of the DWBA theory are in a satisfactory agreement with the theoretical predictions and with the results of previous workers with the only exception of the 2nd excited level in11B.