ANGULAR MOMENTUM POPULATION IN FRAGMENTATION REACTIONS

1
ANGULAR MOMENTUM POPULATION IN FRAGMENTATION
REACTIONS
IoP Nuclear Physics Conference 2009

• Ana M. Denis Bacelar

2
OUTLINE

• Physics motivation
• Theory
• Previous results
• Experimental set-up
• Results
• High spin states
• Isomeric ratios
• Conclusions

3
MOTIVATION

• Extend the knowledge in the neutron-rich N126
  region
• Study of the reaction mechanism of fragmentation
  measuring the population of states with high
  angular momentum in the neutron-deficient N126
  region

Data analysis by Nawras Al-Dahan (U. Surrey)?
Settings around
212Rn, 210Th, 214Th
S347 experiment, GSI
4
THEORY Abrasion-ablation model

• Fragmentation reactions 2 steps
• Abrasion collision between projectile and target
  ? prefragment formed (10-23 s)?

ablation

• Ablation nucleons evaporated ? final fragment
  (10-19 s)?

210-214Th, 212Rn
5
THEORY Abrasion-ablation model
Angular momentum distribution ABRABLA code
(abrasion stage)?

• Spin-cutoff parameter where Af and Ap are
  the masses of the fragment and the initial
  projectile

J.-J. Gaimard and K.-H. Schmidt, Nucl. Phys. A
531 (1991) 709
M. De Jong, A.V. Ignatyuk and K.-H. Schmidt,
Nucl. Phys. A 613 (1997) 435
6
EXPERIMENTALLY

• We can calculate the probability that in a
  reaction a nucleus is produced in an isomeric
  state
• Isomeric ratios (R)?

• We expect

M. Pfützner et al, Phys. Rev. C 65 (2002) 064604
7
PREVIOUS EXPERIMENTS
?
?
Zs. Podolyak et al, Phys. Rev. Lett. 632 (2006)
203
8
PREVIOUS EXPERIMENTS

• Experimental results contradict the model
• An additional source of angular momentum has to
  be considered
• Collective contribution
• Angular momentum abrasion ablation stage

Zs. Podolyak et al, Phys. Rev. Lett. 632 (2006)
203
S. Pal and R. Palit Phys. Lett. B 665 (2008) 164
Better agreement for high spin states
9
EXPERIMENTAL SET-UP

• Accelerator SIS provides a 1 GeV/u 238U beam with
  an intensity of 105 pps (high cross sections)?
• Projectile fragmentation on Be target
• The ions are separated and identified in the FRS

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EXPERIMENTAL SET-UP
Identification in mass and charge in the FRS
ß
SC41
238
SC21
TOF
U
(9Be)?
Stopper
sci43
Dipoles B?
sci42
2
?E Z
11
RESULTS High-spin states in At isotopes
12
RESULTS High-spin states in Rn isotopes
25/2 1 µs 31/2- 1.36 µs
55/2 164 ns ???
8 910 ns 22 109 ns ??? 30 154 ns ???
13
RESULTS High-spin states in 213Rn
Highest spin populated in a fragmentation
reaction !!!
55/2 164 ns ???
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RESULTS Isomeric ratios
PRELIMINARY
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CONCLUSIONS

• Data analysis is going on!
• Several high-spin states were populated
• Test of fragmentation theories
• Useful for production of RIBs at high-spin

215Ra
209At 29/2
211At 39/2
214Ra
213Rn 55/2
210At 19
24
26
28
16
THANK YOU!

• A.M. Denis Bacelar,1 A.M. Bruce,1 Zs.
  Podolyák,2 S. Lalkovski,1 S. Pietri,3 N.
  Al-Dahan,2 M. Górska,3 A. Algora,4 N.
  Alkhomashi,2 J. Benlliure,5 P. Boutachkov,3 A.
  Bracco,10 E.Calore,7 E. Casarejos,5 I.J. Cullen,2
  A.N. Deo,2 P. Detistov,6,9 Z. Dombradi,12 C.
  Domingo-Pardo,3 M. Doncel,6 F. Farinon,3 G.F.
  Farrelly,2 H. Geissel,3 W. Gelletly,2 J. Gerl,3
  N. Goel,3 J. Grebosz,3,8 R. Hoischen,14 I.
  Kojouharov,3 S. Leoni,10 F. Molina,4 A.I.
  Morales,5 D. Montanari,10 A. Musumarra,11 R.
  Nicolini,10 D.R. Napoli,7 C. Nociforo,3
  A.Prochazka,3 P.H. Regan,2 B. Rubio,4 D.
  Rudolph,14 S. Vermas,5 S.J. Steer,2 P.Strmen,13
  T.P.D. Swan,2 I. Szarka,13 J.J. Valiente-Dobón,7
  P.M. Walker,2 H. Weich,3 H.J. Wollersheim3
• 1School of Environment and Technology, University
  of Brighton, Brighton BN2 4GJ, UK
• 2Department of Physics, University of Surrey,
  Guildford GU2 7XH, UK
• 3GSI, Planckstrasse 1, D-64291, Darmstadt,
  Germany
• 4Instituto de Física Corpuscular, Universidad de
  Valencia, E-46071, Spain
• 5Universidad de Santiago de Compostela, E-15706,
  Santiago de Compostela, Spain
• 6Laboratorio de Radiaciones Ionizantes,
  Universidad de Salamanca, E-37008, Spain
• 7 INFN-Laboratori Nazionali di Legnaro, Italy
• 8The Henryk Niewodniczánski Institute of Nuclear
  Physics, PL-31-342, Kraków, Poland
• 9St. Kliment Ohridsky University of Sofia, 1164
  Sofia, Bulgaria
• 10University of Milan
• 11INFN - Laboratori Nazionali del Sud, via
  S.Sofia 62, 95125 Catania, Italy
• 12Institute of Nuclear Research of the Hungarian
  Academy of Sciences, P.O. Box 51, Debrecen,
  H-4001, Hungary
• 13Bratislava Faculty of Mathematics and Physics,
  Comenius University, 84215 Bratislava, Slovak
  Republic
• 14Department of Physics, Lund University, S-22100
  Lund, Sweden