Multi-Nucleon Exchange in Quasi-Fission Reactions

Nucleon exchange mechanism is investigated in the central collisions of ${}^{40}$Ca + ${}^{238}$U and ${}^{48}$Ca + ${}^{238}$U systems near the quasi-fission regime in the framework of the Stochastic Mean-Field (SMF) approach. Sufficiently below the fusion barrier, di-nuclear structure in the collisions is maintained to a large extend. Consequently, it is possible to describe nucleon exchange as a diffusion process familiar from deep-inelastic collisions. Diffusion coefficients for proton and neutron exchange are determined from the microscopic basis of the SMF approach in the semi-classical framework. Calculations show that after a fast charge equilibration the system drifts toward symmetry over a very long interaction time. Large dispersions of proton and neutron distributions of the produced fragments indicate that diffusion mechanism may help to populate heavy trans-uranium elements near the quasi-fission regime in these collisions

Nucleon exchange in heavy-ion collisions within stochastic mean-field approach

Nucleon exchange mechanism is investigated in deep-inelastic symmetric heavy-ion collisions in the basis of the Stochastic Mean-Field approach. By extending the previous work to off-central collisions, analytical expression is deduced for diffusion coefficient of nucleon exchange mechanism. Numerical calculations are carried out for ${}^{40}$Ca + ${}^{40}$Ca and ${}^{90}$Zr + ${}^{90}$Zr systems and the results are compared with the phenomenological nucleon exchange model. Also, calculations are compared with the available experimental results of deep-inelastic collisions between calcium nuclei.Comment: 8 pages, 7 figure

Collisional Damping of Nuclear Collective Vibrations in a Non-Markovian Transport Approach

A detailed derivation of the collisional widths of collective vibrations is presented in both quantal and semi-classical frameworks by considering the linearized limits of the extended TDHF and the BUU model with a non-Markovian binary collision term. Damping widths of giant dipole and giant quadrupole excitations are calculated by employing an effective Skyrme force, and the results are compared with GDR measurements in Lead and Tin nuclei at finite temperature.Comment: 23 pages, 6 Figure

Isovector Collective Response Function of Nuclear Matter at Finite Temperature

We study isovector collective excitations in nuclear matter by employing the linearized Landau-Vlasov equation with and without a non-Markovian binary collision term at finite temperature. We calculate the giant dipole resonance (GDR) strength function for finite nuclei using Steinwedel-Jensen model and also by Thomas-Fermi approximation, and we compare them for 120Sn and 208Pb with experimental results.Comment: 15 pages, 4 figure

Quantal description of nucleon exchange in stochastic mean-field approach

Nucleon exchange mechanism is investigated in central collisions of symmetric heavy-ions in the basis of the stochastic mean-field approach. Quantal diffusion coefficients for nucleon exchange are calculated by including non-Markovian effects and shell structure. Variances of fragment mass distributions are calculated in central collisions of ${}^{40}$Ca + ${}^{40}$Ca, ${}^{48}$Ca + ${}^{48}$Ca and ${}^{56}$Ni + ${}^{56}$Ni systems

Quantum effects in the diffusion process to form a heavy nucleus in heavy-ion fusion reactions

We discuss quantum effects in the diffusion process which is used to describe the shape evolution from the touching configuration of fusing two nuclei to a compound nucleus. Applying the theory with quantum effects to the case where the potential field, the mass and friction parameters are adapted to realistic values of heavy-ion collisions, we show that the quantum effects play significant roles at low temperatures which are relevant to the synthesis of superheavy elements

Merging of transport theory with TDHF: multinucleon transfer in U+U collisions

Multinucleon transfer mechanism in the collision of ${}^{238}\text{U}+{}^{238}\text{U}$ system is investigated at $E_\text{c.m.} =833$ MeV in the framework of the quantal diffusion description based on the stochastic mean-field approach (SMF). Double cross-sections $\sigma(N,Z)$ as a function of the neutron and proton numbers, the cross-sections $\sigma(Z)$ and $\sigma(A)$ as a function of the atomic numbers and the mass numbers are calculated for production of the primary fragments. The calculation indicates the ${}^{238} \text{U}+{}^{238} \text{U}$ system may be located at an unstable equilibrium state at the potential energy surface with a slightly negative curvature along the beta stability line on the $(N,Z)-$plane. This behavior may lead to rather large diffusion along the beta stability direction.Comment: 10 pages, 10 figures. arXiv admin note: text overlap with arXiv:1904.0961

Heavy isotope production in 136Xe+208Pb{}^{136}\text{Xe}+{}^{208}\text{Pb} collisions at Ec.m.=514E_\text{c.m.}=514 MeV

Employing the quantal diffusion mechanism for multi-nucleon transfer, the double differential cross-sections are calculated for production of primary projectile-like and target-like fragments in collisions of ${}^{136}\text{Xe}+{}^{208}\text{Pb}$ system at $E_\text{c.m.} =514$ MeV. Including de-excitation due to neutron emission, the cross-section for production of ${}^{210}\text{Po}$, ${}^{222}\text{Rn}$ and ${}^{224}\text{Ra}$ isotopes are estimated and compared with data.Comment: 7 pages, 3 figures, 2 table

Quantal Diffusion Description of Multi-Nucleon Transfers in Heavy-Ion Collisions

Employing the stochastic mean-field (SMF) approach, we develop a quantal diffusion description of the multi-nucleon transfer in heavy-ion collisions at finite impact parameters. The quantal transport coefficients are determined by the occupied single-particle wave functions of the time-dependent Hartree-Fock equations. As a result, the primary fragment mass and charge distribution functions are determined entirely in terms of the mean-field properties. This powerful description does not involve any adjustable parameter, includes the effects of shell structure and is consistent with the fluctuation-dissipation theorem of the non-equilibrium statistical mechanics. As a first application of the approach, we analyze the fragment mass distribution in $^{48}\mathrm{Ca}+{}^{238}\mathrm{U}$ collisions at the bombarding energy $E_{\text{c.m.}}=193$ MeV and compare the calculations with the experimental data.Comment: 15 pages, 8 figures, 2 tables. arXiv admin note: text overlap with arXiv:1706.0356