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Angular momentum population in fragmentation reactions

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

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Angular momentum population in fragmentation reactions

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  1. Angular momentum population in fragmentation reactions Zsolt Podolyák University of Surrey

  2. Isomers observed following fragmentation of 208Pb and 238U (Z>60) 7 ~15(+3) 5(+5) >20(+7) 2 No. of isomers known(+new) New isomers => nuclear-structure Known isomers => reaction mechanism (angular momentum population What is the production cross section for individual states?

  3. “Power” of fragmentation Low spin ~1 ms PROTON RICH I=43/2

  4. isomeric ratio: ● 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.

  5. Abrasion-ablation model (1-2/3) k = 2 A>10 De Jong, Ignatyuk, Schmidt, NP A613 (1997) 435. “sharp cut-off” approximation:

  6. Analytical formulae ABRABLA M. Pfützner et al., Phys. Rev. C 65 (2002) 054604.

  7. ρth-all states with spin higher than the isomer decay into the isomer

  8. M. Pfützner et al., Phys. Rev. C 65 (2002) 054604. Rexp /ρthe open symbol: known higher-lying isomer (not observed)

  9. Nuclear structure has to be considered 196Pb 270 ns 2.7 MeV 12+ 196Pb: A.K.Singh et al., Nucl. Phys. A707 (2002) 3 186W(16O,6n) at 110 MeV; 170Er(30Si,4n) at 144 MeV fusion-evaporation reaction! 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!

  10. 179W populated in: fragmentation of 208Pb at 1 GeV/u fusion evaporation: 170Er(13C,4n) at 67 MeV

  11. preliminary The highlighted points: Higher lying isomers decay into our isomer

  12. preliminary 177Ta 175Hf 176Ta 179Ta The highlighted points: Higher lying isomers decay into our isomer

  13. 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 Future: There are new data on: 212Fr 15– 213Fr 29/2+ 212Ra 8+ 214Ra 17– 215Ra 43/2– <= HIGHEST SPIN from fragmentation 215Ac 29/2+ 217Ac 29/2+

  14. To be simulated by P. Detistov Surrey/Sofia

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