1. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 1 Two-component (neutron/proton) statistical description of low-energy heavy-ion reactions E. Běták & M. Veselský Institute of Physics, Slovak Academy of Sciences 84511 Bratislava, Slovakia

2. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 2 Introduction Deep-inelastic – effect of neutron/proton composition at periphery Time scales of the processes Possible playground for pre-equilibrium

3. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 3

4. 4 Experiments: 86 Kr on 64 Ni, 112,124 Sn at 25 A MeV: - observed excess of exp. yields of neutron-rich nuclei with Z=32-34 (sometimes in wider range) -explainable within DIT, but better fit with scaled transfer probabilities (for details: Veselský, Souliotis: Nucl. Phys. A765 (2006), 252)

5. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 5 Standard DIT ( Tassan-Got & Stefan, NPA 524 (1991) ) 86 Kr + 64 Ni at 25 AMeV Solid - GEMINI, dash-SMM

6. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 6 Correlation of skin thickness to isovector chemical potential (V. Kolomietz et al, PRC 64(2001)024315, extended Thomas-Fermi calculation)   R n -R p determines the difference of N/Z at (R n +R p )/2 ( surface ) from the bulk N/Z, correlates to isovector chemical potential  DIT (T-G) : macroscopic formula for R n -R p used, values unrealistically large, but bulk N/Z dynamics described well

7. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 7 Modified DIT (Veselský & Souliotis: Nucl.Phys. A765 (2006)): phenomenological correction, effect of shell structure on nuclear periphery (assuming R n -R p vs.  n -  p correlation) and thus on transfer probabilities estimated as: where  S... = S... exp - S... ld,  is a free parameter (  = 0.53 determined as optimal value), s > 0 fm (only non-overlapping configurations considered)

8. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 8 Modified DIT (Veselský & Souliotis: Nucl. Phys. A765) 86 Kr + 64 Ni at 25 AMeV solid - GEMINI, dash -SMM

9. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 9 DIT Conclusions - 86 Kr + 64 Ni, 112,124 Sn at 25 AMeV - a microscopic correction to macroscopic DIT describes the effect of isospin asymmetry at nuclear periphery - inversion of the bulk isospin flow due to microscopic structure at nuclear periphery - consistent parameters  for all reactions - SMM reproduces the yields of n-rich species well while overestimating the yields of  -stable isotopes close to the projectile - GEMINI typically overestimates the width of mass distributions - for p-rich target 112 Sn stronger Coulomb interaction supresses the effect of isospin asymmetry at nuclear periphery at s < 1 fm

10. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 10 Time scale (example):

11. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 11

12. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 12

13. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 13 Pre-equilibrium (exciton model – master eq.): -initial excited zone should follow the Z/N composition of overlapping region – importance of surfaces -initial number of excitons can be estimated from the overlap of nuclei in momentum space at higher energies and at lower energies (below 5 or 10 A MeV above Coulomb)

14. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 14 Inclusion of spin - HIC: (Běták: Fizika B12 (2003), 11)

15. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 15 Pre-equilibrium exciton model suitable instrument to describe the effect of the neutron/proton composition of the initial overlapping region. Features: - model estimates of n 0 - spin- and energy- distributions of initial phase - spin couplings as necessary - includes also equilibrated (CN) emission

16. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 16 Thank you

17. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 17

18. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 18 Experiments at fragment separator MARS ( Cyclotron Lab, Texas A&M University ).

19. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 19 86 Kr + 124 Sn at 25 AMeV Standard DIT ( Tassan-Got ) solid - GEMINI, dash -SMM

20. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 20 86 Kr + 124 Sn at 25 AMeV Modified DIT (nucl-th/0507026): solid - GEMINI, dash -SMM

21. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 21 86 Kr + 112 Sn at 25 AMeV Standard DIT ( Tassan-Got ) solid - GEMINI, dash -SMM

22. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 22 86 Kr + 112 Sn at 25 AMeV Modified DIT (nucl-th/0507026): solid - GEMINI, dash -SMM Dash-dotted - SMM, s > 0.8 fm

23. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 23 86 Kr + 64 Ni at 25 AMeV, Exp. vs. Sim. vs Sim. ICF-only

24. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 24 Isoscaling in nuclear processes M.B. Tsang et al., PRL 86(2001)5023 G. Souliotis et al., PRC 68(2003)24605 M. Veselský et al., PRC 69(2004)44607