description of experimental fission barriers of heavy nuclei i.introduction ii.experimental barriers...
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Description of experimental fission barriers of heavy nuclei
I. IntroductionII. Experimental barriersIII. Method of descriptionIV. Deformation space V. Results and discussion VI. Conclusions
15th Nuclear Physics Workshop: 70 Years of Nuclear FissionSept. 24-28, 2008, Kazimierz Dolny, Poland
M. Kowal, L. Shvedov and A. Sobiczewski
Sołtan Institute for Nuclear Studies, Warsaw, Poland
I. Introduction
1. Region of our interest: SHN (Z=104-126)
2. Motivation: cross sections (~1 pb ~50 fb) Bfst
3. Present state of HN : (map of SHN)
3. Role of Bfst
- sensitivity of to Bfst
- a need for a large accuracy of Bfst
4. Two configurations important for Bfst
- eq. and s.p. (example of fission barrier)5. Concentration on even-even nuclei
98
99
100
101
102
103
104
Db 267Db 267
115 287115 287 115 288115 288
113 283113 283 113 284113 284
111 279111 279 111 280111 280
Mt 275Mt 275 Mt 276Mt 276
Bh 271Bh 271 Bh 272Bh 272
120120120120
119119119119
118118118118
117117117117
116116116116
115115115115
114114114114
113113113113
112112112112
111111111111
Hs 264Hs 264
Ds 267Ds 267
Mt 266Mt 266
111 272111 272
Mt 268Mt 268
Hs 266Hs 266 Hs 267Hs 267
Bh 262Bh 262 Bh 264Bh 264
Sg 263Sg 263
Bh 267Bh 267Bh 266
Db 263Db 263
Rf 263Rf 263
Es 248 Es 249 Es 250 Es 251 Es 252 Es 253 Es 254 Es 255 Es 256Es 256
Fm 249 Fm 250 Fm 251 Fm 252 Fm 253 Fm 254 Fm 255 Fm 256
Md 250 Md 251 Md 252 Md 253 Md 254 Md 255 Md 256 Md 257
Fm 257 Fm 258Fm 258 Fm 259Fm 259
Md 258 Md 259 Md 260Md 260
No 251 No 253 No 254 No 255 No 256 No 257 No 258
Lr 252 Lr 253 Lr 254 Lr 255 Lr 256 Lr 257 Lr 258 Lr 259
No 259 No 260No 260
Lr 260 Lr 261 Lr 262Lr 262
Rf 253 Rf 254 Rf 256 Rf 257 Rf 258 Rf 259 Rf 260
Db 257 Db 258 Db 259
Rf 261 Rf 262 Rf 267Rf 267 Rf 268Rf 268
Db 262 Db 268
Sg 258 Sg 259 Sg 260 Sg 261 Sg 262
Bh 261
Sg 265Sg 265 Sg 266Sg 266 Sg 271Sg 271
Hs 265 Hs 270Hs 270 Hs 275Hs 275
Ds 269 Ds 270Ds 270 Ds 271Ds 271 Ds 279Ds 279 Ds 281Ds 281
112 282112 282 112 283112 283 112 284112 284 112 285112 285
114 286114 286 114 287114 287 114 288114 288 114 289114 289
116 290116 290 116 291116 291 116 292116 292 116 293116 293
118 294118 294
CfCfCfCf
EsEs
FmFm
MdMd
NoNo
LrLr
RfRf
DbDbSgSg
BhBhHsHs
MtMtDsDs
No 262No 262
Cf 247Cf 247 Cf 248Cf 248 Cf 249Cf 249 Cf 250Cf 250 Cf 251Cf 251 Cf 252Cf 252 Cf 253Cf 253 Cf 254Cf 254 Cf 255Cf 255 Cf 256Cf 256
Rf 255
Db 260 Db 261
No 252
Db 256
160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 149 150 151 152 153 154 155 156 157 158 159
105
106
107
108
109
110
113 278113 278
112 277112 277
111 274111 274
Ds 273Ds 273
Mt 270Mt 270
Hs 269Hs 269
II. Experimental barriers
• 1. Bexp for only nuclei closest to SHN are used (Z=92-98)• 2. They are derived from exp in not a very direct way (a model• is used)• 3. Estimated uncertainty: about 0.3-0.4 MeV (?)
III. Method
Macro-micro (same as used for description of many properties of HN) Etot = Emacr + Emicr Emacr = Yukawa + exp Emicr = shell corr.
IV. Deformation space
1. As large as possible
2. Larger space, better description of the properties
(e.g. mass, especially Bfst and Tsf)
3. Specification of the space: axial, non-axial and reflection-asymmetric
shapes included
V. Results
1. Comparison between Bth and Bexp for few variants of calculations in the Z=92-98 region
2. Comparison between Bth for few variants of calculations in a large region of nuclei
138 140 142 144 146 148 1503
4
5
6
7
8 Exp(Smirenkin 93) Moeller et al. (08) Present
Bf(M
eV)
N
Z=92
136 138 140 142 144 146 148 150 152 1543
4
5
6
7
8 Exp(Smirenkin 93) Moeller et al.(08) Present
Bf(M
eV)
N
Z=94
144 146 148 150 152 154 1563
4
5
6
7
8
Exp(Smirenkin 93) Moeller et al. (08) Present
Bf(M
eV)
N
Z=96
136 140 144 148 152 156 160 164 1683
4
5
6
7
8
Mamdouh et al. (01) Moeller et al. (08) Present
Bf(M
eV)
N
Z=98
136 140 144 148 152 156 160 164 168 172 1760
1
2
3
4
5
6
7
8
Mamdouh et al. (01) Moeller et al. (08) Present
Bf(M
eV)
N
Z=104
136 144 152 160 168 176 184 1920
1
2
3
4
5
6
7
8
Mamdouh et al. (01) Moeller et al. (08) Present
Bf(M
eV)
N
Z=110
168 176 184 1920
1
2
3
4
5
6
7
8
9
10
Mamdouh et al. (01) Moeller et al. (08) Present
Bf(M
eV)
N
Z=116
VI. Conclusions
1. It is hard to say how accurately Bexp are determined (0.3-0.4 MeV?) in the U-Cf region.
2. The average inaccuracy of theoretical description of Bexp is rather large (about 0.6-0.8 MeV).
3. Discrepancy between various theor. descriptions in the SHN is very large( up to more than 5 MeV !).
– Not comfortable situation for people calculating σ.– More study is needed.
138 140 142 144 146 148 1503
4
5
6
7
8 Exp(Smirenkin 93) Dobrowolski et al. (07) Mamdouh et al. (98)
Bf(M
eV)
N
Z=92
136 138 140 142 144 146 148 150 152 1543
4
5
6
7
8
Exp(Smirenkin 93) Dobrowolski et al. (07) Mamdouh et al. (98)
Bf(M
eV)
N
Z=94
144 146 148 150 152 154 1563
4
5
6
7
8
Exp(Smirenkin 93) Dobrowolski et al. (07) Mamdouh et al. (98)
Bf(M
eV)
N
Z=96
150 152 154 1563
4
5
6
7
8
Exp(Smirenkin 93) Dobrowolski et al. (07) Mamdouh et al. (98)
Bf(M
eV)
N
Z=98
Conclusions
1. Shapes and shell correction of HN have been studied at two configurations: equil. (ground state) and saddle point.
2. For an accurate study, a large deformation space is needed (10-dimensional space has been used).
3. Equil. config.: - the shapes are axially- and reflection-symmetric for all studied nuclei - shell correction is large (up to about 9 MeV for a doubly magic def. nucleus with
Z=108, N=162 and a spherical one with Z=114, N=184).
4. Sadlle-point config.: - shapes are generally non-axial, but reflection sym.; only lighter nuclei (around
uranium and below) are reflection asym. at their saddle point. - shell corr., although smaller than at equil., is still large (up to about 2.5 MeV). It
should not be disregarded (as quite often done). - effect of non-axiality is large, up to more than 2 MeV. This is a big effect, if one
keeps in mind that a 1 MeV change in Bfst changes the calculated σ by one order of
magnitude or even more.