Accueil du site > Publications récentes > Violent fluctuations in fluids of neutrons and protons explain how atomic nuclei disintegrate
P. Napolitani and M. Colonna
Perturbing fluids of neutrons and protons (nuclear matter) may lead, as
the most catastrophic effect, to the rearrangement of the fluid into
clusters of nucleons.
A similar process may occur in a single atomic nucleus undergoing a
violent perturbation, like in heavy-ion collisions tracked in particle
accelerators at around 30 to 50 MeV per nucleon : in this conditions,
after the initial collision shock, the nucleus expands and then
clusterizes into several smaller nuclear fragments.
Microscopically, when violent perturbation are applied to nuclear
matter, a process of clusterization arises from the combination of
several fluctuation modes of large-amplitude where neutrons and protons
may oscillate in phase or out of phase.
The imposed perturbation leads to conditions of instability, the
wavelengths which are the most amplified have sizes comparable to small
atomic nuclei.
We found that these conditions, explored in heavy-ion collisions,
correspond to the splitting of a nucleus into fragments ranging from
Oxygen to Neon in a time interval shorter than one zeptosecond
(10^-21s).
From the out-of-phase oscillations of neutrons and protons another
property arises, the smaller fragments belonging to a more volatile
phase get more neutron enriched : in the heavy-ion collision case this
process, called distillation, reflects in the isotopic distributions of
the fragments.
The resulting dynamical description of heavy-ion collisions is an
improvement with respect to more usual statistical approaches, based on
the equilibrium assumption. It allows in fact to characterize also the
very fast early stages of the collision process which are out of
equilibrium.
Voir en ligne : Phys. Rev. C 96, 054609
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