Energy Dependence of the Isotopic Composition in Nuclear

Fragmentation

S. Yennello, D. Shetty, M. Veselsky, E. Martin, A. Keksis, G. Souliotis and

D. Rowland

Texas A&M University

Cyclotron Institute

Single component liquid

Two component liquid

Possible signatures:Free n/p ratiot/3He ratioN/Zfragments

Two component liquid

124Sn 124Sn

Veselsky, Phys. Rev. C 62, 064613 (2000).

0 100 200

100

0 50 100 150 200 250

100

0 50 100 150 200 250

10

100

0 50 100 150 200 250

10

100

(50MeV/nuc)

E*

QP, MeV

Co

un

ts (

arb

. u

nits

)

Co

un

ts (

arb

. u

nits

)

E*

QP, MeV

(30MeV/nuc)

E*

QP, MeV

Veselsky, Phys. Rev. C 62, 064613 (2000).

28Si + 112,124SnE*=2.5-3.5 E*=3.5-4.5 E*=4.5-5.5

E*=5.5-6.5 E*=6.5-7.5 E*=7.5-8.5

E*=8.5-9.5 E*=9.5-10.5 E*=10.5-12.5

Veselsky,Phys Lett B 497,1(2001)

QPZNaa

HeY

HY213

3

ln

Ratio of isotopic yields58Ni, 58Fe + 58Ni, 58Fe 30 Mev/nuc

ZNCeZNR ),(21

Scaling factor

ZeRS 21

Relative free neutron and proton densities

NiNinn

/

NiNipp

/

Scaling factor at 30,40,47 MeV/nuc

neutron and proton densities at 30,40,47 MeV/nuc

NiNinn

/

NiNipp

/

Energy dependence of the scaling parameter

30 MeV 40 MeV 47 MeV

0.372 0.269 0.23

-0.395 -0.372 -0.32

0.15

0.2

0.25

0.3

0.35

0.4

25 30 35 40 45 50

Beam Energy ( MeV/nuc)

alp

ha

.

Tsang PRC64, 054615 (2002)

58Fe + 58Fe / 58Ni + 58Ni

Botvina IsoscalingR21 = C exp(’A + ’(N-Z)

30 MeV/nuc 50 MeV/nuc

’ = 0.237±0.038 ’ = 0.186±0.017

’ = (n + p)/2T

’ = (n - p)/2T

28Si + 112,124Sn

Botvina IsoscalingR21 = C exp(’A + ’(N-Z)

28Si + 112,124Sn ; 50 MeV/nuc

E*

(MeV)

’

3 0.31

4 0.20

5 0.19

6 0.18

7 0.17

Summary

• The enhancement in free neutrons of neutron-rich systems is greater at lower energies.– Isoscaling in 58Ni, 58Fe + 58Ni, 58Fe– 3H/3He in 28Si + 112Sn, 124Sn– Isoscaling in 28Si + 112Sn, 124Sn

Chomaz PLB 47, 221 (1999)

Baran Nucl Phys 1999

Bao An Li PRL 2000

Theory

Summary

• The enhancement in free neutrons of neutron-rich systems is greater at lower energies.– Isoscaling in 58Ni, 58Fe + 58Ni, 58Fe– 3H/3He in 28Si + 112Sn, 124Sn– Isoscaling in 28Si + 112Sn, 124Sn

• Theoretical comparisons are in progress.

This work was supported in part by the Department of Energy and the Robert A Welch Foundation