Download - Angular momentum population in fragmentation reactions Zsolt Podolyák University 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?
● 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
isomer
NNR 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. Pfützner et al., Phys. Rev. C 65 (2002) 054604.
Rex
p /ρ
the
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+
prelim
inary
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: