GOSIA as a tool for COULEX on exotic beams

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GOSIA as a tool for COULEX on exotic beams

• Katarzyna Wrzosek
• Heavy Ion Laboratory
• Warsaw University

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LOW - ENERGY COULOMB EXCITATION

• Well-established method to study collective
  excitations in nuclei.
• Purely electromagnetic ? the only nuclear
  properties involved are the matrix elements of
  the electromagnetic multipole moments.

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208Pb

• Gamma ray spectrometer
• EXOGAM up to 11 segmented Ge clovers (90? and
  135?)
• Particle detector
• CD-detector - annular, highly segmented double
  silicon strip detector (DSSD)covered angles
  23,8?-54,5? in the LAB 24?-145? in the C.M.
  frame

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COULEX Analysis Scheme
Measured? yields
Experimental setup geometryparticle and ?
detectors
Level scheme
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GOSIA

• GOSIA is a Rochester Warsaw semiclassical
  coupled-channel Coulomb excitation least-squares
  search code.
• Developed in early eighties by T. Czosnyka, D.
  Cline, C.Y.Wuand continuously upgraded to
  fulfill requirements of new experiments.
• Used extensively for Coulomb excitation studies
  of a wide range of nuclei.
• Typical use of GOSIA
• Fitting of the matrix elements to the
  experimental data.
• Simulation of the experimentsto predict which
  ? - ray will be observedto check to what extent
  the observation will depend on individual matrix
  elements.

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AN EXAMPLECOULOMB EXCITATION OF 74,76Kr _at_ GANIL

• Coulomb excitation is the only method that can
  directly distinguish between different shapes of
  the nucleus ? ideally suited to verify the shape
  coexistence scenario in the Kr isotopes.
• Shape parameters of the two lowest 0 states in
  74Kr and 76Kr nuclei were inferred from coulomb
  excitation data.
• The Coulomb excitation analysis were performed
  using the last squares fitting code GOSIA.

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EXPERIMENTS (SPIRAL _at_ GANIL)
74Kr
76Kr
76Kr 208Pb(106 pps, 4.4A MeV)
74Kr 208Pb (5105 pps, 4.7A MeV)
E. Clement et al., submitted to Phys Rev C
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76 Kr
76Kr
71.0 - 87.7
107.0 - 121.5
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RESULTS
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QUADRUPOLE ROTATIONAL INVARIANT SUM RULES model
independent description of the nuclear shape

• is based on a fact, that scalar products of
  E2 operators are rotational invariants. Operator
  products may be expressed using the intermediate
  state expansion formula

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QUADRUPOLE ROTATIONAL INVARIANT SUM RULES model
independent description of the nuclear shape

• To get information on triaxiality the higher
  order invariant is needed

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RESULTS

• The deformation of the 01 is very similar in
  74Kr and 76Kr.
• Triaxiality parameter
• the ground state of 76Kr is prolate, while the
  02 state has an triaxial shape.
• Both, the ground state and the 02 state of 74Kr
  are triaxial, but with different ? parameter.

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Collaboration of 74,76Kr Project

• CEA Saclay, France
• E.Clément
• A.Görgen
• W.Korten
• E.Bouchez
• A.Chatillon
• A.Hürstel
• Y.Le Coz
• A.Obertelli
• Ch.Theisen
• J.N.Wilson
• CEA/DIF, France
• J.-P. Delaroche
• M.Girod
• H.Goutte
• S.Péru
• GANIL, Caen, France
• J.M.Casandjian
• G. de France

• HIL Warsaw, Poland
• T.Czosnyka
• J.Iwanicki (OLL, Liverpool)
• P.J.Napiorkowski
• M.Zielinska (CEA Saclay)
• Oliver Lodge Lab., Liverpool, UK
• C.Andreoiu
• P.A.Butler
• R.-D.Herzberg
• D.G.Jenkins
• G.D.Jones
• Univ. Of Surrey, Guildford, UK
• W.N.Catford
• C.Timis
• GSI, Darmstadt, Germany
• F.Becker
• J.Gerl
• NBI, Copenhagen, Denmark
• G.Sleten

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List of the experiments where GOSIA was recently
used

• ISOLDE (MINIBALL), CERN
• J. Cederkall 108Sn, 110Sn
• J. Iwanicki - 88Kr, 92Kr
• A. Hurst - 70Se
• I. Stefanescu 68Cu, 70Cu
• J. Van de Walle 74Zn
• GANIL (EXOGAM), FRANCE
• E. Bouchez 76Kr
• E. Clement 74Kr
• M. Zielinska 44Ar
• JYVASKYLA, FINLAND
• F. Becker 78Kr
• JAEA, TOKAI, JAPAN
• M. Koizumi - 66Zn, 68Zn
• T. Hayakawa 78Se
• A. Osa - 84Kr
• Y. Toh 70Ge
• M. Zielinska 96Mo
• ANL (Gammasphere), USA

• Next experiments
• ISOLDE (MINIBALL), CERN
• E. Clement 96Sr (Jul 2007)
• P.Butler, P. Van Duppen - 182,184Hg (Aug 2007)

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Warsaw Coulomb Excitation Group_at_ Heavy Ion
Laboratory, Warsaw Univ.

• Tomasz Czosnyka
• Julian Srebrny
• Jedrzej Iwanicki
• Pawel Napiorkowski
• Magdalena Zielinska (CEA Saclay)
• Katarzyna Wrzosek
• Katarzyna Hadynska (UAM, Poznan)
• Daniel Pietak (PW, Warsaw)

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Thank you