comparison of rotating finite range model and thomas-fermi fission barriers
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Comparison of Rotating Finite Range Model and Thomas-Fermi Fission barriers. K. Mahata Nuclear Physics Division Bhabha Atomic Research Centre Mumbai –400 085, INDIA. Plan of the talk. Introduction Fission barrier models Compound nucleus formation and decay - PowerPoint PPT PresentationTRANSCRIPT
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Comparison of Rotating Finite Range Model
and Thomas-Fermi Fission barriersK. Mahata
Nuclear Physics Division
Bhabha Atomic Research Centre
Mumbai –400 085, INDIA
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Plan of the talk
Introduction
Fission barrier models
Compound nucleus formation and decay
Statistical model of CN decay
Discrepancy in fold distribution measurement
Inconsistency in fold distribution and cross-section
Summary an conclusion
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En
erg
y
Bf
Fission barrier which inhibit fission results from near cancellation of surface and Coulomb energy.
Single particle effects
Angular momentum dependence
Compound nucleus formation
Competition between the fission and the particle evaporation channel
saddle point shape determine the angular distribution of fission fragments.
Introduction
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Rotating Liquid Drop Model (1974):
Potential energies and equilibrium configuration of a rotating uniformly charged incompressible fluid with sharp boundary.
Bf required to reduce by a factor varying between 0.5 to 0.9
extracted eff were found to be larger.
Rotating Finite Range Model (1986):
Finite range effects in the nuclear surface energy
Finite surface diffuseness effects in the Coulomb energy and effective moment of inertia.
Thomas-Fermi Model (1996):
Effective two-body interaction were adjusted to fit shell-corrected masses, diffuseness of nuclear surface and depth of optical model potential
Fission barrier model
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Angular momentum dependence
27
14)0(
)0()(22 2/
J
f
Jff
MeVB
eBJB J
Thomas-Fermi fissionbarrier falls faster than RFRM fission barrier
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TargetP
CN
ER Saddle
FF FF
Scission
Compound nucleus formation and decay
n p
J()
E*
Fu
s(J)
(J) xn
Fission
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Statistical Model for the decay of compound nucleus
All possibilities for decay are equally likely
Governed and T.
dEJE
jET
hdEsjEJER
sj
sjS
SJ
SJl ii
flfii
i
i
|| || ),(
),()(
1),,;,(
Def.
E*
Important input
Bf
af/an
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48Ca + 142Nd 190Hg 80Se + 110Pd
B. Djerroud et al., PRC 61, 024607 (2000)
Discrepancy in fold distribution
Enhancement of the high-spin population for the more symmetric system, brought in by the coupling to inelastic channels.
No enhancement was observed.
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Fold distribution cont…
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ER-fission data not availableAvailable for 40Ar + 148Sm 188Hg (similar to 48Ca + 142Nd)ER data for 86Kr + 104Ru 190Hg(similar to 80Se + 110Pd)
What happens to ER-fission cross-section
Reisdorf et al., NPA444 (1985) 154 Reisdorf et al., NPA438 (1985) 212
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Entry Spin distribution
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Sensitivity of the fission and the ER excitation function
Use of Thomas-Fermi fission barriers produces good agreement
RFRM fission barrier has to be reduced by a factor 0.85
Inclusion of –3 MeV shell correction in Thomas-Fermi fission barriers produces large discrepancy
ER-fission data and fold distribution data are not consistent
The accuracy of fission barrier height can be checked by comparing the measured fission and ER cross-sections with the statistical model predictions.
Effort should be put to parameterize Thomas-Fermi barrier
Summary & Conclusion