Characterizing Neutron-Proton Equilibration in Nuclear Reactions with Subzeptosecond Resolution

Transport properties of isospin asymmetric nuclear matter using the time-dependent Hartree-Fock method

“…The fact that (N/Z) values of the fragments are not exactly equal, even in fully damped collisions, is not a signature for being out of isospin equilibrium [13]. Indeed, the thermodynamic equation of state indicates that the fragments should approach a common chemical potential (in our case strongly affected by symmetry energy) rather than a common composition.…”

“…An equilibration time τ ∼ 0.5 zs is obtained from the fit (N − Z)/A = α + β exp(−T /τ). Recently, Jedele et al [13] obtained a slightly faster equilibration time of ∼ 0.3 zs from experimental data at Fermi energy. The fact that TDHF gives a charge equilibration time of the same order indicates that it incorporates the essential physics to describe this process.…”

“…For example, collisions at Fermi energies give access to contact times which are short enough to induce only a partial charge equilibration [12] and thus can be used to determine equilibration times [13]. Alternatively, charge equilibration has also been studied with deep inelastic collisions at lower energies, but with large isospin asymmetry in the entrance channel [14][15][16].…”

Exploring Zeptosecond Quantum Equilibration Dynamics: From Deep-Inelastic to Fusion-Fission Outcomes in Ni58+Ni60Williams1, Sekizawa2, Hinde3 et al. 2018Phys. Rev. Lett.455550View full textAdd to dashboardCite

“…Through the manipulation of collision entrance channel parameters (projectile-target combinations and energies), a range of factors with the potential to affect energy dissipation can be explored. Typical timescales for energy dissipation in such systems could in principle vary from isospin and mass equilibration times on the order of 0.3-0.5 zs [14,15] and ∼5 zs [16,17], respectively.In nuclear reactions, the observation of the total kinetic energy of the reaction products (TKE) offers a direct measure of energy dissipation. The observation of the masses of reaction products via direct or indirect methods offers a measure of system equilibration in a key degree of freedom, and can be used to explore fluctuations in reaction product masses as a function of TKE.…”

“…Through the manipulation of collision entrance channel parameters (projectile-target combinations and energies), a range of factors with the potential to affect energy dissipation can be explored. Typical timescales for energy dissipation in such systems could in principle vary from isospin and mass equilibration times on the order of 0.3-0.5 zs [14,15] and ∼5 zs [16,17], respectively.…”