Non-thermal projectile breakup due to friction forces

Projectile break-up with two outgoing intermediate-mass fragments in 26 AMeV32S+197Au

“…Moreover, as the heavier primary fragments certainly do not have larger mean excitations energies [14] they even less favour channels yielding carbon-carbon pairs, too, as the more complex decay would require more energy for the separation of more particles. The same tendency is implied by our observation [19] that emission probabilities decrease with increasing primary PLF mass. This is reflected both by the mean multiplicity of sequential e particles going down steadily from 0.35 for oxygen to 0.01 for silicon fragments and by the IMF multiplicities decreasing, too, with increasing total (primary fragment) mass.…”

“…2, 3) reminds of the same feature as observed in particle emission [12,19] where it was taken as qualitative manifestation of the direct break-up mode in the sense of the dynamical model [10,18] described in the next section: in a deep-peripheral collision, the target-distant part of the projectile is only slightly deflected and decelerated (and hits the trigger, in our case), while the target-close part by the strong friction force is separated from the remainder, decelerated and bent around the target nucleus in an orbiting trajectory.…”

“…2 with those in Fig. 1 of [19]), whereas in studies of the statistical decays of nuclei like 24Mg* produced in low-energy fusion [16] or (e, e') [17] they could hardly be detected. We take this as an indication for a different production mode and try to quantify this observation for the example of the 'ac-~2C channel for which information on the possible 24Mg* mother decays are available [16,17].…”

“…Information on mean excitation energies is provided by the emission energy distributions of sequentially emitted particles which can be fitted with Maxwell distributions and yield temperatures in the range of 2 to 3 MeV for all PLFs [ 19]. This corresponds to a mean excitation of about 25 MeV for primary Mg fragments decaying with c~ par- Curve."…”

“…rays. From the proton multiplicity [19] for carbon of at most 0.4 one may estimate a neutron multiplicity of 0.6, or 1.2 neutrons for the pair, representing roughly 15 MeV. The ?…”