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Shell Effects in Atomic Nuclei Forewords Few-body systems Heavier systems Summary Shell Eects in Atomic Nuclei Laurent Gaudefroy1 Alexandre Obertelli2 1CEA, DAM, DIF - France 2CEA, Irfu - France Shell Eects in Finite Quantum Systems Erice-Sicily July 25-31, 2010 logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 1/37 Forewords Few-body systems Heavier systems Summary The atomic nucleus General properties Z Protons: Jπ = 1/2+; N Neutrons: Jπ = 1/2+; A = N + Z fermions. Strong interaction range: ' 2 fm 1/3 Nuclear radius: R ' r0A fm, r0 ' 1.2 fm. Nucleon mean free path: > R. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 2/37 Forewords Few-body systems Heavier systems Summary From nucleon-nucleon to nuclear interaction Nuclei description Strong short-range repulsion; A (N+Z) interacting fermions; Ab initio approach Nuclear mean eld Created by the (A-1) nucleons; Replaces NN-interaction. Shell Model or Mean Field approaches. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 3/37 Forewords Few-body systems Heavier systems Summary Magic numbers: 2, 8, 20, 28, 50, 82, 126 Goeppert Mayer & Jensen From M. Goeppert Mayer Nobel Lecture (1963) "What makes a number magic is that a conguration of a magic number of neutrons, or of protons, is unusually stable whatever the associated number of the other nucleons.[. ] We found that there were a few nuclei which had greater isotopic as well as cosmic abundance than our theory or any other reasonable theory could explain. Then I found those nuclei had something in common: they either had 82 neutrons, [. ] or 50 neutrons." logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 4/37 Forewords Few-body systems Heavier systems Summary Spin-Orbit interaction Harmonic oscillator potential 1 2 2 U(r) = 2 Mω r Magic numbers: 2, 8, 20, 40, 70 Angular momentum and spin-orbit U 0 (r) = U(r) + `2 + `s Magic numbers: 2, 8, 20, 28, 50, 82 logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 5/37 Forewords Few-body systems Heavier systems Summary Success and failure of the nuclear shell model Good features 1 Accounts for known magic numbers. 2 Reproduces Jπ, E ∗, Q, µ... Bad features 1 Built from knowledge on stable nuclei. 2 (Dis)appearance of magic numbers in unstable nuclei. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 6/37 Forewords Few-body systems Heavier systems Summary Outline Today 1 Few body systems. Haloes. Clusters. 2 Heavier systems. Shell evolution: general view. Studies at N = 28. Tomorrow 1 Shapes and coexistence. 2 Super heavy elements. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 7/37 Forewords Few-body systems Heavier systems Summary Few-body systems Why? 1 3 1 Nuclear interaction ∝ A− / 2 Strong shell eects expected 3 Exotic phenomena Haloes Clusters logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 8/37 From 40Ca to 42Ca ⇒ No signicant change. idem for 44Ca. 20 neutrons latter ρ(r > 2) %. Forewords Few-body systems Heavier systems Summary Density distributions in He isotopes S.C. Pieper & R.B. Wiringa Annu. Rev. Nucl. Part. Sci.51, 53(2001). Add 2 neutrons to 4He ⇒ ρ(r > 2) % factor of 10. 6 8 He ' He logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 9/37 idem for 44Ca. 20 neutrons latter ρ(r > 2) %. Forewords Few-body systems Heavier systems Summary Density distributions in He isotopes S.C. Pieper & R.B. Wiringa Annu. Rev. Nucl. Part. Sci.51, 53(2001). Add 2 neutrons to 4He From 40Ca to 42Ca ⇒ ρ(r > 2) % factor of 10. ⇒ No signicant change. 6 8 He ' He logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 9/37 20 neutrons latter ρ(r > 2) %. Forewords Few-body systems Heavier systems Summary Density distributions in He isotopes S.C. Pieper & R.B. Wiringa Annu. Rev. Nucl. Part. Sci.51, 53(2001). Add 2 neutrons to 4He From 40Ca to 42Ca ⇒ ρ(r > 2) % factor of 10. ⇒ No signicant change. 6 8 44 He ' He idem for Ca. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 9/37 Forewords Few-body systems Heavier systems Summary Density distributions in He isotopes S.C. Pieper & R.B. Wiringa Annu. Rev. Nucl. Part. Sci.51, 53(2001). Add 2 neutrons to 4He From 40Ca to 42Ca ⇒ ρ(r > 2) % factor of 10. ⇒ No signicant change. 6 8 44 He ' He idem for Ca. logocea logocea 20 neutrons latter ρ(r > 2) %. L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 9/37 Forewords Few-body systems Heavier systems Summary Halo nuclei An exotic phenomenon Weakly bound nuclei. Extension of neutron wave function out of the interaction range! Linked to shell structure (s or p waves). logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 10/37 Does not follow A1/3 law for: (6,8He), 11Li, 11,14Be and 17B. (Near) Drip line nuclei. Forewords Few-body systems Heavier systems Summary Halo nuclei: Experimental evidence R from reaction cross section: 2 σ = π(RTarget + RProj ) . logocea I. Tanihata, J. Phys. G: Nucl. Part. Phys.22, 157 (1996). logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 11/37 Forewords Few-body systems Heavier systems Summary Halo nuclei: Experimental evidence R from reaction cross section: 2 σ = π(RTarget + RProj ) . Does not follow A1/3 law for: (6,8He), 11Li, 11,14Be and 17B. (Near) Drip line nuclei. logocea I. Tanihata, J. Phys. G: Nucl. Part. Phys.22, 157 (1996). logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 11/37 Drip-line Loosely bound systems Low ` e−Snr Ψ(r) ∝ r . Centrifugal force. Forewords Few-body systems Heavier systems Summary Halo nuclei: Shell eect logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 12/37 Forewords Few-body systems Heavier systems Summary Halo nuclei: Shell eect Drip-line Loosely bound systems Low ` S r r e− n . Centrifugal force. Ψ( ) ∝ r logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 12/37 Forewords Few-body systems Heavier systems Summary Halo nuclei: Shell eect Drip-line Loosely bound systems Low ` r e−Snr . Ψ( ) ∝ r Centrifugal force. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 13/37 Structural eect 15 22 From C9 to C16 ⇒ νs1/2 orbit as GS. Not yet quantitatively understood. Forewords Few-body systems Heavier systems Summary Halo nuclei: Shell eect Structural eect From N = 9 to N = 14: νd5/2 lling. Strong shell eect ⇒Shell rearrangement. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 14/37 Structural eect From N = 9 to N = 14: νd5/2 lling. Strong shell eect ⇒Shell rearrangement. Forewords Few-body systems Heavier systems Summary Halo nuclei: Shell eect Structural eect 15 22 From C9 to C16 ⇒ νs1/2 orbit as GS. Not yet quantitatively understood. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 14/37 Forewords Few-body systems Heavier systems Summary Halo nuclei Summary 1 Extension of nucleon wave function out of interaction range. 2 Appear in light loosely bound nuclei. 3 Shell eects ⇒ orbital reordering. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 15/37 Forewords Few-body systems Heavier systems Summary Density distribution in 8Be. −16 Unbound GS: T1/2 ' 10 s ⇒8 Be →4He + 4He. 0+: two structures ⇒4He cluster. α: N = Z = 2. Clusters might appear in light N = Z nuclei. R. B. Wiringa et al., Phys. Rev. C 62, 014001 (2000). logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 16/37 Forewords Few-body systems Heavier systems Summary Clusters in nuclei Energy threshold for clustering Must be energetically allowed. 8Be → 2α 4nX → nα Cluster phase expected around E ∗ = decay threshold. K. Ikeda et.al, Prog. Theor. Phys. (Suppl.), 464. logocea (1968) logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 17/37 Forewords Few-body systems Heavier systems Summary Clusters & Shell eects Adapted from: M. Freer, Rep. Prog. Phys. 70, 2149 (2007). logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 18/37 Forewords Few-body systems Heavier systems Summary Clusters & Shell eects Adapted from: M. Freer, Rep. Prog. Phys. 70, 2149 (2007). logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 18/37 Forewords Few-body systems Heavier systems Summary Clusters & Shell eects Adapted from: M. Freer, Rep. Prog. Phys. 70, 2149 (2007). logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 18/37 Forewords Few-body systems Heavier systems Summary Clusters & Shell eects Adapted from: M. Freer, Rep. Prog. Phys. 70, 2149 (2007). logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 18/37 Forewords Few-body systems Heavier systems Summary Clusters in nuclei. Summary α clusters appear in N=Z light nuclei. Close to decay threshold. Strong deformation leading to shell rearrangement. Experimental evidence: Eg. look for deformed structure. logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 19/37 Triple α process: Fowler (Nobel Prize 1983). Forewords Few-body systems Heavier systems Summary Digression: 12C, life and clusters. Synthesis of 12C Insucient production for 12C; F. Hoyle (1954) predicted a ' 7.27 MeV state logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 20/37 Forewords Few-body systems Heavier systems Summary Digression: 12C, life and clusters. Synthesis of 12C Insucient production for 12C; F. Hoyle (1954) predicted a ' 7.27 MeV state Triple α process: Fowler (Nobel Prize 1983). logocea logocea L. Gaudefroy, A. Obertelli Shell Eects in Atomic Nuclei 20/37 Forewords Few-body systems Heavier systems Summary Few Body Systems Summary 1 Benchmarks for models.
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