Angular momentum population in fragmentation reactions
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Angular momentum population in fragmentation reactions Zsolt Podolyák University of Surrey
description
Angular momentum population in fragmentation reactions. Zsolt Podolyák University of Surrey. Isomers observed following fragmentation of 208 Pb and 238 U (Z>60). 7. ~15(+3). 5(+5). >20(+7). 2. No. of isomers known(+new). New isomers => nuclear-structure - PowerPoint PPT Presentation
Transcript of Angular momentum population in fragmentation reactions
Angular momentum population in fragmentation reactions
Zsolt PodolyákUniversity of Surrey
2
~15(+3)
>20(+7)
5(+5)
7
Isomers observed following fragmentation of 208Pb and 238U (Z>60)
No. of isomersknown(+new)
New isomers => nuclear-structureKnown isomers => reaction mechanism (angular momentum population
What is the production cross section for individual states?
I=43/2
Low spin
PROTON RICH
~1 ms
“Pow
er”
of fr
agm
enta
tion
● M. Pfützner et al., Phys. Lett. B444 (1998) 32. ■ M. Pfützner et al., Phys. Rev. C65 (2002) 064604.▲ K. Gladnishki et al., Phys. Rev. C69 (2004) 024617.
isomeric ratio:
total
isomerN
NR exp
Abrasion-ablation model
(1-2/3)
k = 2 A>10
“sharp cut-off” approximation:
De
Jong
, Ign
atyu
k, S
chm
idt,
NP
A61
3 (1
997)
435
.
]2
)1(exp[)( 2
mJ f
mmth
JJdJJPR
M. P
fütz
n er e
t al .,
Ph y
s . R
e v. C
65
(20 0
2 ) 0
5 46 0
4.
ABRABLA
Analytical formulae
ρth -all states with spin higher than the isomer decay into the isomer
M. Pfützner et al., Phys. Rev. C 65 (2002) 054604.R
exp
/ρth
e
open symbol: known higher-lying isomer (not observed)
Nuclear structure has to be considered
φ = Iisomer/(I parallel+I isomer) = Iisomer / I total
ρexp=Rexp /φ
ρexp - the probability of populating states with higher spin than the isomer – can be compared with theory!
196Pb: A.K.Singh et al., Nucl. Phys. A707 (2002) 3186W(16O,6n) at 110 MeV; 170Er(30Si,4n) at 144 MeV fusion-evaporation reaction!
196Pb
270 ns 2.7 MeV 12+
179W populated in: fragmentation of 208Pb at 1 GeV/u fusion evaporation: 170Er(13C,4n) at 67 MeV
The highlighted points: Higher lying isomers decay into our isomer
preliminary
preliminary
175Hf
176Ta179Ta
177Ta
The highlighted points: Higher lying isomers decay into our isomer
Conclusions on the reaction mechanism
• Good agreement between experiment and theory (within a factor of 2-3)
• predictions for radioactive beams seems to be possible
There are new data on:212Fr 15– 213Fr 29/2+
212Ra 8+
214Ra 17–
215Ra 43/2– <= HIGHEST SPIN from fragmentation215Ac 29/2+ 217Ac 29/2+
Future:
Background from the stopping down of the fast ions:
To be simulatedby P. Detistov Surrey/Sofia
