chemical instability in heavy ion collisions at high and intermediate energies
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Chemical instability in heavy ion collisions at high and intermediate energies. Z.Q. Feng( 冯兆 庆 ), W.F. Li( 李文飞 ), Z.Y. Ming( 明照宇 ), L.W. Chen( 陈列文 ), F. S. Zhang ( 张丰收 ) Institute of Low Energy Nuclear Physics Beijing Normal University Tel: 010-6220 8252 Fax: 010-6223 1765

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chemical instability in heavy ion collisions at high and intermediate energies

Chemical instability in heavy ion collisions at high and intermediate energies

Z.Q. Feng(冯兆庆), W.F. Li(李文飞),

Z.Y. Ming(明照宇), L.W. Chen(陈列文),

F. S. Zhang (张丰收)

Institute of Low Energy Nuclear Physics

Beijing Normal University

Tel: 010-6220 8252

Fax: 010-6223 1765

E-mail: [email protected]

outline
Outline

1 Introduction

2 Isospin dependent quantum molecular dynamics model

3 Isospin effects in nuclear multifragmentation

4 Chemical and mechanical instabilities

5 Conclusions and perspectives

1 introduction
1 Introduction

Experimental status

 p(1GeV)+Kr, Xe, Ag, 1984

 excited nuclei(4 detector)

 Aladin, Au (600 MeV/nucl.) +X

<MIMF> Zbound

 Miniball, Xe (30 MeV/nucl.)+X

<NIMF> NC, NLC, NN

 Indra, Ar(32-95 MeV/nucl.)+X

Xe(25-50 MeV/nucl.)+X

 etc.

Nuclear Multifragmentation, Zhang and Ge, Science Press, 1998

slide7
 Isospin effects in nuclear multifragmentation

 induced by radioactive ion beams (RIB facilities)

GANIL, GSI, MSU, Riken, IMP, 

 induced by stable nuclei with large neutron excesses(Accelerator with ECR source)

slide8
MSU, 1996-1998

 112,124Sn(40MeV/nucl.)+112,124Sn

isospin effects in multifragmentation

 58Fe(45-105 MeV/nucl.)+58Fe,

58Ni(45-105 MeV/nucl.)+58Ni,

disappearance of isospin effects in multifragmentation

 Physical indications and challenges

 0, T > 0,  >0

E(, T, ) = ?

Important to production of RIB &Neutron Stars !!!

slide9
G. J. Kunde et al., 112,124Sn(40MeV/nucl.)+112,124Snisospin effects in multifragmentation,<NN>~NC ,<NIMF>~NC, <NIMF>~NN
slide10

G. J. Kunde et al., isospin effects in multifragmentation224,248100X(*=1.3-10 MeV), <NIMF>~NN ,<NIMF>~NC, <NIMF>~NLC, EES model

slide11

G. Kortemeyer et al.Percolation model just regenerate the isospin effects in the relationship of <NIMF> ~NN, but not for <NIMF> ~ NC

slide12
M. L. Miller et al. Disappearance of isospin dependence of multifragmentation prooduction58Fe(Ni)+58Fe(Ni), at 45-105 MeV/n
2 isospin dependent quantum molecular dynamics model
2 Isospin dependent quantum molecular dynamics model

Quantum molecular dynamics model (QMD)

The QMD model represents the many body state of the system and thus contains correlation effects to all orders.In QMD, nucleon i is represented by a Gaussian form of wave function.

After performing Wigner transformations, the density distribution of nucleon i is:

slide14
From QMD model & IQMD model

 mean field (corresponds to interactions)

Uloc : density dependent potential

UYuk: Yukawa (surface) potential

UCoul: Coulomb energy

USym: symmetry energy

UMD: momentum dependent interaction

slide15
 two-body collisions

 Cugnon’s parameterization:

np =nn= pp

 Experimental data:

NN is isospin dependent,

for Ebeam < 300 MeV/nucl.,

np  3nn=3pp

slide16
 Pauli blocking:

the Pauli blocking of n and p is treated separately

Initialization:

 in real space: the radial position of n and p are sampled by using MC method according to the n and p radial density distribution calculated from SHF (or RMF) theory

 in momentum space: local Fermi momentum is given by

slide18
 Coalescence model:

 physics:

ri-rj R0, pi-pj P0

R0=3.5 fm, P0=300 MeV/c

 geometry:

Rrms 1.14 A1/3

 reality:

comparing the isotope calculated with the nuclear data sheets

3 isospin effects in nuclear multifragmentation
3 Isospin effects in nuclear multifragmentation

 4 analyzing

b=1, 2, 3, 4, 5, 6, 7, 8, 9, 10 fm

the number events is proportional to b

 statistics: t  200 fm/c, the charge distribution have been stable. One selects fragments over t=200-400 fm/c

average n multiplicity n n as a function of charged particle multiplicity n c
Average n multiplicity <NN>, as a function of charged-particle multiplicity NC
averaged number of imf n imf as a function of n c n lc and n n 4 pre equilibrium emissions
Averaged number of IMF <NIMF>as a function of NC, NLC,and NN (4  pre equilibrium emissions)
averaged number of mf n imf as a function of z bound 4 and 4 pre equilibrium emissions

Chapter 10:“Isospin-Dependent Quantum Molecular Dynamics

Model and Its Applications in Heavy Ion Collisions,”

Isospin Physics in Heavy Ion Collisions at Intermediate Energies,

ed. By Li and Schrode, Nova Science Publishers Inc.,New York,2001

Averaged number of MF <NIMF>as a function of Zbound (4 and 4  pre-equilibrium emissions)
slide25

Averaged number of MF <NIMF>as a function of Zbound (4 and 4  pre-equilibrium emissions)

Chapter 10:“Isospin-Dependent Quantum Molecular Dynamics

Model and Its Applications in Heavy Ion Collisions,”

Isospin Physics in Heavy Ion Collisions at Intermediate Energies,

ed. by Li and Schrode, Nova Science Publishers Inc,New York,2001

4 chemical and mechanical instabilities
4 Chemical and mechanical instabilities
  • (E/ T),0
  • thermodynamical instability
  • (P/ )T,<0
  • mechanical instability
  • (volume, surface, Coulomb instabilities)
  • (n/ )P,T<0
  • chemical instability
isotopic distributions of ne a 17 32 for central collisions at 40 and 100 mev nucl
Isotopic distributions of Ne (A=17 ~32) for central collisions at 40 and 100 MeV/nucl.

---------- 112Sn+112Sn

_______ 124Sn+124Sn

slide30

Origin of multifragmentation:

mechanical or/and chemical instabilities ?

slide33

Origin of multifragmentation:

mechanical or/and chemical instabilities ?

slide34

Li and Schroder , book in 2001

61 MeV

61 MeV

61 MeV

50.6 MeV

5 conclusions and perspectives
5 Conclusions and perspectives

Theoratical Models

phenomenological :

 expanding evaporating model

 percolation model

 statistical multifragmentation model

microscopic:

 isospin dependent quantum molecular dynamics model

 Boltzmann-like model, such as IBL

 isospin dependent far from equilibrium model

slide37
Experimental

signals of chemical instability

 isospin effects in multifragmentation

 propose more physical observable

sensitive to chemical instability ?

nuclear reactions induced byradioactive ion beams

 neutron-rich

 neutron-poor

 n-halo nuclei

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