Two component neutron proton statistical description of low energy heavy ion reactions
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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. Introduction Deep-inelastic – effect of neutron/proton composition at periphery

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Two-component (neutron/proton) statistical description of low-energy heavy-ion reactions

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Two component neutron proton statistical description of low energy heavy ion reactions

Two-component (neutron/proton)statistical descriptionof low-energy heavy-ion reactions

E. Běták & M. Veselský

Institute of Physics, Slovak Academy of Sciences

84511 Bratislava, Slovakia

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


Two component neutron proton statistical description of low energy heavy ion reactions

  • Introduction

  • Deep-inelastic – effect of neutron/proton composition at periphery

  • Time scales of the processes

  • Possible playground for pre-equilibrium

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


Two component neutron proton statistical description of low energy heavy ion reactions

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


Two component neutron proton statistical description of low energy heavy ion reactions

Experiments: 86Kr on 64Ni, 112,124Sn 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)

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


Two component neutron proton statistical description of low energy heavy ion reactions

86Kr + 64Ni at 25 AMeV

Standard DIT ( Tassan-Got & Stefan, NPA 524 (1991) )

Solid - GEMINI, dash-SMM

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


Two component neutron proton statistical description of low energy heavy ion reactions

Correlation of skin thickness to isovector chemical potential

(V. Kolomietz et al, PRC 64(2001)024315, extended Thomas-Fermi calculation)

- Rn-Rp determines the difference

of N/Z at (Rn+Rp)/2 ( surface ) from the bulk N/Z, correlates to isovector chemical potential

- DIT (T-G) : macroscopic formula

for Rn-Rp used, values unrealistically large, but bulk N/Z dynamics described well

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


Two component neutron proton statistical description of low energy heavy ion reactions

Modified DIT (Veselský & Souliotis: Nucl.Phys. A765 (2006)):

phenomenological correction, effect of shell structure on nuclear periphery (assuming Rn-Rp 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)

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


Two component neutron proton statistical description of low energy heavy ion reactions

86Kr + 64Ni at 25 AMeV

Modified DIT (Veselský & Souliotis: Nucl. Phys. A765)

solid - GEMINI, dash -SMM

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


Two component neutron proton statistical description of low energy heavy ion reactions

DIT Conclusions - 86Kr + 64Ni, 112,124Sn 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 112Sn stronger Coulomb interaction supresses

the effect of isospin asymmetry at nuclear periphery at s < 1 fm

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


Two component neutron proton statistical description of low energy heavy ion reactions

Time scale (example):

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


Two component neutron proton statistical description of low energy heavy ion reactions

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


Two component neutron proton statistical description of low energy heavy ion reactions

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


Two component neutron proton statistical description of low energy heavy ion reactions

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)

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


Two component neutron proton statistical description of low energy heavy ion reactions

Inclusion of spin - HIC:

(Běták: Fizika B12 (2003), 11)

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


Two component neutron proton statistical description of low energy heavy ion reactions

Pre-equilibrium exciton model suitable instrument to describe the effect of the neutron/proton composition of the initial overlapping region.

Features:

- model estimates of n0

- spin- and energy- distributions of initial phase

- spin couplings as necessary

- includes also equilibrated (CN) emission

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


Thank you

Thank you

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


Two component neutron proton statistical description of low energy heavy ion reactions

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


Two component neutron proton statistical description of low energy heavy ion reactions

Experiments at fragment separator MARS ( Cyclotron Lab, Texas A&M University ).

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


Two component neutron proton statistical description of low energy heavy ion reactions

86Kr + 124Sn at 25 AMeV

Standard DIT ( Tassan-Got )

solid - GEMINI, dash -SMM

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


Two component neutron proton statistical description of low energy heavy ion reactions

86Kr + 124Sn at 25 AMeV

Modified DIT (nucl-th/0507026):

solid - GEMINI, dash -SMM

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


Two component neutron proton statistical description of low energy heavy ion reactions

86Kr + 112Sn at 25 AMeV

Standard DIT ( Tassan-Got )

solid - GEMINI, dash -SMM

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


Two component neutron proton statistical description of low energy heavy ion reactions

86Kr + 112Sn at 25 AMeV

Modified DIT (nucl-th/0507026):

Dash-dotted - SMM, s > 0.8 fm

solid - GEMINI, dash -SMM

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


Two component neutron proton statistical description of low energy heavy ion reactions

86Kr + 64Ni at 25 AMeV, Exp. vs. Sim. vs Sim. ICF-only

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


Two component neutron proton statistical description of low energy heavy ion reactions

M.B. Tsang et al., PRL 86(2001)5023

G. Souliotis et al., PRC 68(2003)24605

Isoscaling in nuclear processes

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

M. Veselský et al., PRC 69(2004)44607


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