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  • 004

    1. 1. Sez.-CT GDR pre-equilibrium emission 40Ca+48Ca,46Ti at 25 MeV/A S.Tudisco EPL 58 (5), 811(2003) M.Papa et al, PRC 68., 034606 (2003) F.Amorini et al PRC 69, 014608(2004) Fusion-Incomplete Fusion Dissipative binary processes Extra yield at 10 MeV
    2. 2. GDR pre-equilibrium emission 40Ca+48Ca,46Ti at 10 MeV/A M.Papa et al, submitted to PRC Dissipative binary processes study of kinematical coincidence
    3. 3. Z=14-22 Elab<160 MeV 40Ca+46Ti 40Ca+46Ti γ-1f γ-2f 40Ca+48Ca
    4. 4. CoMD calculations TKEL-angular and charge distrib. b-window→ pre-eq γ Yield
    5. 5. How we can generate the coherent Sez.- contribution? CT A simple picture the “Molecular Dipole” The average ensemble in an harmonic mean field The initial conditions for the GDR mode At the contact D1≈D2 ≈0 n p N1/Z1≠N2/Z2 if If Y=0 NO coherent contribution
    6. 6. Sez.-CT Coherent contribution Incoherent contribution (ensemble average) a) Collective b) Microscopic incoherent Mean field approach Statistical models Fully N-body dynamical approach for 1000 fm/c
    7. 7. Υ-ray average multiplicity in Sez.-CT Semi classical Approximation The Larmor formula Fourier Transform
    8. 8. b=0 fm E/A 25 MeV Sez.-CT Langevin prediction for the total system ∗Prediction in the loc. Time equil. hypothesis • Prediction according to a full CoMD approach g~12 M.Papa et al, PRC 68(2003) 034606
    9. 9. We have also high energy Sez.-CT bremsstrahlung contribution We have to study the 1. We need to define T at long time local time 2. We need to separate the spectral properties of incoherent Microscopic contribution
    10. 10. Sez.-CT High energy results Multifragmentation of the hot source
    11. 11. M.Papa et al, PRC 50 MeV/A b=0 fm Sez.-CT 68(2003) 024612 ∗ • α obtained from the fit procedure Very small or Coherent contribution
    12. 12. Something is changed in the fundamental properties of the formed hot sources…. Degree of collectivity-Degree of coherence as function of t
    13. 13. A new observable related to the properties of the dipolar γ-ray emission in different reaction mechanisms has been measured - Φch represents the ratio between the average and fluctuating dynamics. For N-body approaches able to evaluate the two contributions in a self consistent way, this parameter should be rather robust with respect some model ansatz: semiclassical approximaton, occupation numbers……. - On the other hand and we can expect that Φch can depend on the dynamics (Forces) governing the equilibration Process. From the experiments Фch(12MeV)=0.6±0.15 10 MeV/A Binary. proc. Фch(10 MeV)=0.3±0.07 25 MeV/A Inc. fusion.proc.
    14. 14. Collectivity and Coherence for the total system limiting energy for the collective motion M.Papa et al, PRC 68(2003) 024612, Black: rather smooth behaviour 40Ca + 48Ca Central Collisions Red:it contains the Ambiguity related to the experimental *10 selections of 1 equilibrated source Green:high sensitivi Φc(0,tm) ty, related to the Φc(0,tf) natural time selection Φch(0,tf) performed by the dynamic through memory effects.
    15. 15. CoMD calculations TKEL-angular and charge distrib. b-window→ pre-eq γ Yield
    16. 16. γ-Pre-equilibrium effects and “Isospin-Equlibration” M.Papa et al Sub. PRC Invariant with respect to secondary statistical emission processes
    17. 17. Conclusive remarks Sez.-CT 1. An unified description of the pre-equilibrium phenomenon (fluctuating average dynamics) has been obtained throgh ComD calculations 2. 2. The fluctuation predicted by the model are in agreement with Cascade calculations at 25 MeV/A by using g≈12. 2. φch rapidly change when the multifragmentation processes set in. (much more than φc) 3. The pre-equilibrium extra-yield it is strictly related to the isospin equilibration process throgh a quasy-resonant mechanisms.

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