the fission barriers of superheavy and exotic nuclei fedir a. ivanyuk 1 and krzysztof pomorski 2 1...
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![Page 1: THE FISSION BARRIERS OF SUPERHEAVY AND EXOTIC NUCLEI Fedir A. Ivanyuk 1 and Krzysztof Pomorski 2 1 Institut for Nuclear Research, Kiev, Ukraine 2 Theoretical](https://reader030.vdocuments.net/reader030/viewer/2022032800/56649d405503460f94a19937/html5/thumbnails/1.jpg)
THE FISSION BARRIERS OF SUPERHEAVY
AND EXOTIC NUCLEI
Fedir A. Ivanyuk1 and Krzysztof Pomorski2
1Institut for Nuclear Research, Kiev, Ukraine2Theoretical Physics Division, UMCS, Lublin, Poland
• The variational principle for liquid drop shapes
• The account of curvature energy• The fission barriers within LSDrop model• The semi-analytical expression for the barrier
heights based on the topological theorem• Numerical results, mass-asymmetric shapes• Summary and outlook
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2
0max
( )( , ) ( )exp
( )LSD
I I ZB Z I B Z
I Z
28 30 32 34 36 380
10
20
30
barr
ier
heig
ht (
MeV
)
Z2 / A
Bexp
BLSD
-Emicr
(gs)
B LSD micrV = + E ,B
• For Emicr see P. Moeller, J. R. Nix,
• W. D. Myers and W. J. Swiatecki, • At. Data and Nucl. Data Tables, • 59, 249 (1995).
2 4max 0 1 2 3
0 4 5
26 7 8
( ) ,
( )
( )
B Z a a Z a Z a Z
I Z a a Z
I Z a a Z a Z
• The rms-deviation is 1.113 MeV for known nuclei withZ>70
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V.M.Strutinsky et al, Nucl. Phys. 46, 659 (1963)
1 2 12
212
( ) profile function
0
2( )
LD LD surf Coul curv
LD
E E y E y E y E y
E V Ry
R y z z
y y
z
z
dV
2
1
2
1
2surf
22
Coul
2 2 3/2
( )
1 2
0) (0 2
1 ( ) 10
2 ( ) 1 ( / )
1 ( )( ) ( , ( ))
2
the fissility parameter, / 2 ( / ) / 49
( ) the
( ) (1 ( )
Coulomb pot ti
)
en
L
z
z
z
LD Sz
LD LD C S
S
S
D
E y z dy dz dz
dy zE x y z z y
yy y y
z dzdz
x x E E Z
x
z
z z y
A
al on the surface
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Optimal shapes
-2 -1 0 1 2
-1
0
1
xLD
=0.75
y(z)
/R0
z / R0
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Deformation energy
xLD
=1.0
xLD
=0.0
1.0 1.5 2.0 2.5-0.1
0.0
0.1
0.2
0.3
Ede
f / E
(0) su
rf
R12
/ R0
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R.W.Hasse, W.D.Myers, Geometrical Relationships of Macroscopic Nuclear Physics:
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Modified Funny Hills shape parametrization
0.5 1.0 1.5 2.0 2.5
0.000
0.005
0.010
0.015
xLD
=0.75
Ede
fLD /
Esu
rf
(0)
R12
/ R0
MFH, B-minimization "optimal" shapes
2 22 2
0
2
2 3 4
1( ) (1 )(1 ),
( , )
( ) / ,
3( , ) 1 ( 1/2 ) Erf ( )4 2
1,
( ) 8.4977 24.893 25.566 10.836 1.6624
a u
sh
y z u u Becf a B
u z z cR
B af a B e a a aa
a
B c c c c c
• deviation < 150 keV
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Surface curvature energy
Leptodermous expansion:
ETF = Evol+ Esurf + Ecurv + EGcurv
1.0 1.5 2.0 2.5
0.00
0.05
0.10
0.15
0.20
0.25
0.75
0.65
0.5
0.3xLD
=0.15
/R0= 0.05
Ede
fLD/ E
(0) su
rf
R12
/ R0
2 2 2 3/21 2
(0)
0
1 2
(0)
20
(0)
20
(0) (0)
( )4
1 1 1( )
2
4
(
[1 ( ) ], ( ) [1 ( ) ]
1 )4
/
curvcurv
SS
SS curv
curv S
EE H z dS
R
H zR R
EE dS
R
EE E H dS
R
E E
R y y R y y
3/22 2 2 21 2(1 / ( ) ) 1 ( ) 10 1 ( )LD Syy y yy y y z x yy
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The LSD barrier heights
0.1 0.2 0.3
0
5
10
15
20
25
90
85
80
105
10095
Z=75
BLS
D /
MeV
(N-Z)/A
0.0 0.1 0.2 0.3
20
30
40
50
60
40
50
60
7065
55
45
Z=35
BLS
D /
MeV
(N-Z)/A
2 4max 0 1 2 3
0 4 5
26 7 8
( ) ,
( )
( )
B Z a a Z a Z a Z
I Z a a Z
I Z a a Z a Z
2
0max
( )( , ) ( )exp
( )LSD
I I ZB Z I B Z
I Z
F.A.Ivanyuk and K.Pomorski, Phys: Rev. C 79, 054327 (2009)
2
2 2/3
2 1/3
2 2 2
41/30
(1 )
(1 ) ( )
(1 ) ( )
3( )
5
LSD vol vol
surf surf S
curv curv K
Cch
E b I A
b I A B def
b I A B def
Z e ZB def C
Ar A
K.Pomorski and J. Dudek, Phys. Rev. C 67, 044316 (2003)
The rms dev.for 35<Z< 105, 0<I< 0.3 is 150 keV
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The barrier heights, topological theorem
28 30 32 34 36 380
10
20
30
barr
ier
heig
ht (
MeV
)
Z2 / A
Bexp
BLSD
-Emicr
(gs)
(saddle) (saddle) (g.s.) (g.s)B LSD LSDV = E +δE -E +δE
W. D.Myers and W. J. Swiatecki, Nucl. Phys. A601, 141 (1996): the “barrierwill be determined by a path that avoids positive shell effects and has no use for negative shell effects. Hence the saddle point energy will be close to what it would have been in the absence of shell effects, i.e., close to the value given by the macroscopic theory!”
(saddle)B LSD micr
(g.s) (g.s.) (sph)micr LSD LSD
V = V + E ,
E =δE +( E -E )
• For Emicr see P. Moeller, J. R. Nix, W. D. Myers and W. J. Swiatecki,
At. Data and Nucl. Data Tables, 59, 249 (1995).
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Barriers of light nuclei
10 12 14 16 18 20 22 24 26 28 30 32 34 36 380
10
20
30
40
50
60
barr
ier
heig
ht (
MeV
)
Z2 / A
Bexp
BLSD
-Emicr
(gs)
75Br35 , 90Mo42 , 94 Mo42 , 98Mo42
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Mass asymmetry
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
ELD
=EC+E
S
0.7
0.6
0.5
0.4
0.3
0.1
0.2
xLD
=0L
D-b
arr
ier
he
igh
t /
ES
(0)
(MR-M
L)/(M
R+M
L)
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The temperature dependence of the LSD-barriers
B. Nerlo-Pomorska, K. Pomorski and J. Bartel, Phys. Rev. C 74, 034327 (2006)
1.0 1.5 2.0-4
-2
0
2
4
232ThT=0
5
4
3
2
1
Ede
f(LS
D)
(MeV
)
R12
/ R0
2
2/3
1/3 2 1/3
( , ) ( , ) ( , ), ( , ) 2
( , ) ln (1 )ln(1 )
( , ) ( , ), ( , ) ( , 0)
/ 0.092 0.036 ( )
0.275 ( ) 0.00146 / (
Yukawa folded mean field
k kk
k k k kk
surf
curv Coul
F N T E N T T S N T E N T n
S N T n n n n
F N T F N T F N T F N T aT
a MeV A A B def
A B def Z A B def
% % %
2
)
( , , ) ( , 0, ) ( )LSD LSDF N T def F N T def a def T
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Summary• The optimal shapes of fissioning nuclei are studied within the Lublin-
Strasbourg drop model
• The liquid drop fission barriers were calculated for isotopic chains in the range 35< Z < 110 and a simple approximation for the liquid drop fission barriers heights containing only Z and (N-Z)/A is obtained.
• The topological theorem by Myers and Swiatecki was used to express the fission barrier height as the sum of the macroscopic barrier height and the ground-state shell correction. This provides a very simple method to calculate fission barrier heights. In addition to the ground-state shell
• correction, which should be taken from the tables, one only has to calculate simple analytical estimate for the liquid drop part of the barrier height.
• The rms deviation of calculated versus experimental values of fission-barrier heights for known nuclei with Z < 70 is 1.113 MeV, a value that is comparable with the experimental uncertainties.
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• Dear colleagues,• This is the first circular of the 3-rd International Conference on Current Problems• in Nuclear Physics and Atomic Energy (NPAE-Kyiv2010), which will be held from• June 7 to June 12, 2010 in Kyiv, Ukraine.
• The NPAE-Kyiv2010 conference will cover the following topics:• Collective processes in atomic nuclei• Nuclear reactions• Nuclear structure and decay processes• Rare nuclear processes• Neutron and reactor physics, nuclear data• Problems of atomic energy• Applied nuclear physics in medicine and industry• Experimental facilities and detection techniques
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Mass-asymmetric shapes
1 2 12 3
1 2
21
2 2 3/ 22
0
1 1 1( )
2
as
[1 ( ) ],
(
ymmetry
) [1 ( ) ]
: R L
R L
LD
V
E V Ry
H zR R
R y y
R y y
V
V V
2 * 2 3/ 21 2
*3sign1 ( ) 10( ) ( ) [1 ( ) ]LD Szyy y y z z x z yz
-2 -1 0 1 20,0
0,5
1,0
y(z)
z / R0
-2 -1 0 1 20
1
2
xLD
=0.75
H(z
)
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Mass asymmetric shapes, x = 0.75
0.9
0.6
0.3
R12
/R0
asy
mm
etr
y
0
0.75 1.0 1.25 1.5 1.75 2.0 2.25
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K.T.R.Davies and A.J.Sierk, Phys.Rev.C 31 (1985) 915