Isotopic dependence of nuclear temperatures
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A systematic study of isotope temperatures has been presented for heavy-ion collisions at 600 MeV/nucleon via the isospin-dependent quantum molecular dynamics model in the company of the statistical decay model (GEMINI). We find that the isospin dependence of the isotope temperatures in multifragmentation is weak; however, this effect is still visible over a wide isotopic range. The isotope temperatures for the neutron-rich projectiles are larger than those for the neutron-poor projectiles. We also find that the isotope temperatures calculated by the model decrease with increasing nuclear mass.Fragmentation
Nuclear Structure
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A simple Monte Carlo cascade model giving the exclusive description of the heavy ion collisions is described. Comparison with the data on O+Au collisions at 60 and 200 GeV suggests that in this energy region all secondary particles are produced basically by the multiple cascade collisions of the projectile and target nucleons, while the cascading of the produced particles is rather negligible.
Collision cascade
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The production cross sections of projectile-like fragments from collisions of 15 MeV/nucleon 86Kr with 64,58Ni and 124,112Sn have been measured using a magnetic separator with emphasis on the neutron-rich isotopes. Neutron pick-up isotopes (with up to 6-8 neutrons picked-up from the target) were observed with large cross sections. The present results were also compared with our previous data of the same reactions at 25 MeV/nucleon. The data at 15 MeV/nucleon show enhanced production of neutron-rich isotopes very close to the projectile, relative to the corresponding data at 25 MeV/nucleon. The large cross sections of such reactions involving peripheral nucleon exchange, indicate that these reactions offer a novel route to access extremely neutron-rich rare isotopes towards the the astrophysical r-process path and the neutron-drip line.
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Nucleon-nucleon (NN) cross sections are evaluated in neutron-rich matter using a scaling model according to density, momentum, and isospin dependent nucleon effective masses. It is found that the in-medium NN cross sections are not only reduced but also have a different isospin dependence compared with the free-space ones. Because of the neutron-proton effective mass splitting the difference between nn and pp scattering cross sections increases with the increasing isospin asymmetry of the medium. Within the transport model IBUU04, the in-medium NN cross sections are found to influence significantly the isospin transport in heavy-ion reactions. With the in-medium NN cross sections, a symmetry energy of ${E}_{\mathrm{sym}}(\ensuremath{\rho})\ensuremath{\approx}31.6(\ensuremath{\rho}/{\ensuremath{\rho}}_{0}){}^{0.69}$ was found most acceptable compared with both the MSU isospin diffusion data and the presently acceptable neutron-skin thickness in $^{208}\mathrm{Pb}$. The isospin dependent part ${K}_{\mathrm{asy}}({\ensuremath{\rho}}_{0})$ of isobaric nuclear incompressibility was further narrowed down to $\ensuremath{-}500\ifmmode\pm\else\textpm\fi{}50$ MeV. The possibility of determining simultaneously the in-medium NN cross sections and the symmetry energy was also studied. The proton transverse flow, or even better the combined transverse flow of neutrons and protons, can be used as a probe of the in-medium NN cross sections without much hindrance from the uncertainties of the symmetry energy.
Isobaric process
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Based on the light charged particles and fragments emitted towards forward angles by using the heavy projectile on the light target, we have made use of isospin-dependent quantum molecular dynamics to investigate a sensitive probe on the isospin effects in the process of intermediate energy heavy ion collision. The calculation results show that the correlation between the multiplicity of intermediate mass fragments and the total number of charged par- ticles in the energy region above 80MeV/u is a sensitive probe on the isospin-dependent nu- cleon-nucleon cross section in medium in intermediate energy heavy ion collision, meanwhile the isospin effects of symmetric energy is not obvious in the same energy region.
Multiplicity (mathematics)
Impact parameter
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Probing in-medium nucleon-nucleon (NN) cross section σ1NN (α) in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum-dependent interaction (IMDI(τ)). It is found that there are the very obvious medium effect and the sensitive isospin-dependence of nuclear stopping R on the in-medium NN cross section σ1NN(α) in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of σ1NN(α) in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R's in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of σ1NN(α) because of adding a new judgement.
Mass number
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Multiplicity (mathematics)
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The cross sections for capture, ionization, capture from pair production, and free pair production were measured for 0.96-GeV/nucleon U${}^{92+}$ and 0.405-, 0.96-, and 1.3-GeV/nucleon La${}^{57+}$ ions incident on Au, Ag, and Cu targets. The cross sections for capture from pair production, free pair production, ionization, and total capture (the sum of capture from pair production, radiative electron capture, and nonradiative capture) are analyzed as a function of collision energy, projectile, and target atomic numbers. We find that, when the collision energy is increased from 0.405 GeV/nucleon to 1.3 GeV/nucleon, the capture from pair production and the free pair production cross sections increase by almost a factor of 6, while the capture cross section decreases by two orders of magnitude. The ionization cross section is found to vary very weakly with the collision energy in the 1-GeV/nucleon energy range. We found a dependence of free pair production cross sections on the target and projectile atomic number to be close to ${Z}^{2}$, characteristic of an ionizationlike process. We also found a dependence of the capture from pair production cross sections on the target atomic number to be usually steeper than ${Z}_{t}^{2}$, and on the projectile atomic number, somewhat steeper than the ${Z}_{p}^{5}$, characteristic of a capturelike process. Theory and experiment are in some disagreement for capture from pair production, and free pair production, cross sections, but are in general agreement for the other capture processes and for ionization.
Pair production
Electron capture
Impact parameter
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