The fission of heated nuclei in reactions involving heavy ions: static and dynamical aspects

Macroscopic-microscopic approach to the nuclear fission process

“…Measured mass distributions of heavy fissioning nuclei above the Businaro-Gallone point (i.e., Z 2 /A > 22) from high excitation energies can well be described by a Gaussian distribution. This finding is related to the available number of states above the potential energy as a function of mass asymmetry [32]. The second derivative c A = d 2 U /(dA 1 ) 2 of the potential as a function of the mass of one of the nascent fragments is related to the standard deviation σ A of the mass distribution by the following relation:…”

“…Following this idea, we take the systematics established in ref. [32] using the temperature at saddle in equation (1) for deducing the second derivative c A of the potential from the experimental data. Thus, we have the first quantitative relation, which we use in our model to calculate the width of the mass distribution in case of sufficiently high excitation energies.…”

Mass-energy distribution of fragments in Langevin dynamics of fission induced by heavy ions

“…Here η = 2(M 1 − M 2 )/(M 1 + M 2 ) is the mass-asymmetry coordinate, which was introduced by Strutinsky [23] and which is frequently used in analyzing relevant experimental data [3,4,6] The increase of angular momentum I only slightly increases the stiffness of the nucleus with respect to mass asymmetry, whereas increase of K decreases it more notably. This decreasing of compound nucleus stability with respect to mass asymmetry coordinate after inclusion of K coordinate should make the mass distribution of fission fragments broader with respect to the 3D calculations, where K = 0 is supposed during the fission process.…”

“…In the past decades, extensive experimental investigations performed by research groups from Almaty and Dubna and devoted to exploring mass-energy distributions yielded a vast body of important information. The majority of those experimental studies were systematized and analyzed in the review articles quoted in [3][4][5][6].…”

Fission Dynamics: The Quest of a Temperature Dependent Nuclear Viscosity

“…They are characterized by an evaporation residue (ER) cross-section comparable or larger than the fission cross-section, and by a shorter path in the deformation space from the saddle-to-scission point [21]. Consequently: 1) the input parameters of the models can be further constrained by the energy spectra and multiplicities of the light particles in the ER channel; 2) the effect of the fission delay over the fission and ER cross section is much more pronounced with respect to heavier systems because the emission of a charged particle in the pre-saddle region strongly enhances the probability of producing an evaporation residue as consequence of both a reduction of the fissility 07004-p.3 and the large value of the angular momentum necessary to ignite fission.…”