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Insights into Coulomb Barrier Distributions: Recent Experiments & Puzzles

This study explores various couplings, Q-reaction influences, and deformation parameters in nuclear reactions, aiming to optimize superheavy element production and investigate exotic nuclear structures’ impact on reaction mechanisms. Through experimental methods and theoretical predictions, the research addresses open questions regarding weak channels and barrier structures. Conclusions emphasize the significant influence of weak channels on barrier heights and the need for further investigation and analysis. The collaborative efforts of researchers from multiple institutions aim to advance understanding in the field of nuclear physics.

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Insights into Coulomb Barrier Distributions: Recent Experiments & Puzzles

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  1. Coulomb barrier distributions: puzzles and recent experiments Eryk Piasecki and The Barrier Collaboration September 2006

  2. 58Ni + 60Ni A.M.Stefanini et al., Phys.Rev.Lett. 74(1995)864

  3. Motivation (hopes) • Determination of importance of various couplings (vibrational, rotational, single-particle ones) in different reaction and systems. • What is the influence of the Q of reaction? • What is the influence of formfactors? • Determination of the nuclei deformation parameters (2, 3, 4 and perhaps even 6), including their sign, what is pretty difficult using the standard Coulomb excitation methods. • Reliable calculation of the nucleus-nucleus cross-sections in sub-barrier region. • Optimization of superheavy elements production. • Investigation of the influence of exotic nuclear structures (e.g. “halo”) on the reaction mechanisms.

  4. Two experimental methods:

  5. Are the methods equivalent? H.Timmers et al., NP A 633(1998)421

  6. 16O + 144Sm H.Timmers et al., NP. A584(1995)195

  7. Predictions of Coupled Channels Theory for 20Ne + 118Sn (CCFULL code) Cluster model No couplings Shape of20Ne With couplings b2 = 0.46 b3 = 0.39 b4 = 0.27

  8. What we miss in the calcs??? Suspicion: perhaps the „weak” channels (transfers, s.p. excitations) are not that weak as it is assumed in the CC calculations?

  9. 20Ne + 116Sn p - stripping a - stripping

  10. ~Z1*Z2*b

  11. Estimatedfrom systematics

  12. Estimatedfrom systematics

  13. Expectations & experimental results: 20Ne + 90Zr: weak neutron transfer barrier structure 20Ne + 92Zr: stronger neutron transfer no structure wider barrier distribution

  14. Is the puzzle solved?? • Open questions: • Transfers and/or s.p. exciations? • Quantitative relation between the strength of „weak” channels and barrier smoothing • Why the barrier structure has been observed in many experiments? • Is Dfus as sensitive for smoothing as Dqe? • CC treatment of these problems

  15. Simultaneous measurements of Dfus & Dqe JYU Aug/Sept. 2006

  16. Measurements of weak channels strengths (transfers & s.p. excitations) E MCP START Target beam 20Ne natNi 90,92Zr 118Sn 206,208Pb (E,ToF)  A LToF = 55cm FWHMToF≈ 200ps

  17. SD array Targets MCP

  18. 20Ne + 118Sn 16O 20Ne Time of flight 19Fe 22Ne Energy

  19. Conclusions: • The weak channels can have quite considerable influence on the barrier height distributions • There are still some (interesting) open questions • Transfers and/or s.p. exciations? • Quantitative relation between the strngth of „weak” chanels and barrier smoothing • Why the barrier structure has been observed in many experiments? • Is Dfus as sensitive for smoothing as Dqe? Some of the answers are probably already in our hands and will be presented soon. • CC treatment of these problems is badly needed September 2006

  20. The BARRIERCollaboration: • Warsaw University (Inst. Exp. Phys. & Heavy Ion Lab): • Ł.Świderski, P. & T. Czosnyka, J.Jastrzębski, A.Kordyasz, M.Kowalczyk, M.Kisieliński, K.Piasecki, E.Piasecki • Białystok University:T.Krogulski • Technische Universitat (Darmstadt):M.Mutterer • Radium Institute (St. Petersburg):S.Kchlebnikov, G.Turin • University of Jyvaskyla: W.Trzaska, M. Sillanpää • Tohoku University:K.Hagino • IReS (Strasbourg):N.Rowley • Inst. Nucl. Studies (Warsaw):K.Rusek • LNL (Legnaro):A.Stefanini • LNS (Catania): P.Russotto • JINR (Dubna):E.Kozulin,S.Smirnov • Kurchatov Inst. (Moscow):A.Ogloblin, S.Dmitriev

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