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. 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. Z=14-22 Elab<160 MeV
40Ca+46Ti
40Ca+46Ti
γ-1f γ-2f 40Ca+48Ca

4. CoMD calculations
TKEL-angular and charge distrib.
b-window→ pre-eq γ Yield

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. 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. Υ-ray average multiplicity in Sez.-CT
Semi classical Approximation
The Larmor formula
Fourier Transform

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. 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. Sez.-CT
High energy results
Multifragmentation
of the hot
source

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. Something is changed in the fundamental
properties of the formed hot sources….
Degree of collectivity-Degree of coherence as function of t

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. 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. CoMD calculations
TKEL-angular and charge distrib.
b-window→ pre-eq γ Yield

16. γ-Pre-equilibrium effects and “Isospin-Equlibration”
M.Papa et al Sub. PRC
Invariant with respect to
secondary statistical emission
processes

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.