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Low-Energy Multipole Excitations and Nucleosynthesis in Nuclei

This international school on nuclear physics focuses on studying nuclei in the laboratory and in the cosmos, with a particular emphasis on low-energy multipole excitations and nucleosynthesis. Topics include neutron capture processes, fusion in stars, atomic nucleus response to electromagnetic radiation, and theoretical models for atomic nuclei. Calculation of ground state densities, anharmonicities in nuclear wave functions, and the dynamics of nuclear skin are also discussed.

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Low-Energy Multipole Excitations and Nucleosynthesis in Nuclei

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  1. INTERNATIONAL SCHOOL OF NUCLEAR PHYSICS36th CourseNuclei in the Laboratory and in the CosmosErice-Sicily: September 16-24, 2014 LOW-ENERGY MULTIPOLE EXCITATIONS AND NUCLEOSYNTHESIS Nadia Tsoneva Institut für Theoretische Physik, Universität Giessen

  2. Horst Lenske Triangle Universities Nuclear Laboratory, Durham, USA W. Tornow, A.P. Tonchev,G. Rusev et al. R. Schwengner, F. Donau, S. Frauendorf, E. Grosse P. von Neumann-Cosel , N. Pietralla, A. Richter, D. Savran Institute of Astronomy and Astrophysics (IAA) Université libre de Bruxelles, Belgium A. Zilges, V. Derya, M. Spieker et al. S. Goriely Monash Centre for Astrophysics (MoCA),Australia M. Lugaro N.Tsoneva, ERICE14

  3. Nucleosynthesis of Heavier Elements Heavierelements ( Z> 26-28) canbeassembledwithinstarsbyneutroncaptureprocesses. • Twomainneutroncaptureprocesses • s- process– slowneutroncapture, • lowneutrondensities • r~108/cm3 • life time • t ~ 1 – 10 years • r – process- rapid neutroncaptures • r ~1020/cm3 • …otherprocesses ? p-process r-process s-process Fusion in stars N.Tsoneva, ERICE14

  4. Characteristic Response of an Atomic Nucleus to EM Radiation Pygmy-quadrupole resonance Pygmy-dipole resonance Two-phonon excitation Giant M1 resonance Giant Dipole Resonance E1 (GDR) Scissors mode Spin-flip M1 21+ 31- E (MeV) Theoretical prediction of Pygmy Quadrupole Resonance: N. Tsoneva, H. Lenske, Phys. Lett. B 695 (2011) 174. N.Tsoneva, ERICE14

  5. The Theoretical Model Quasiparticle-Phonon Model: V. G. Soloviev: TheoryofAtomicNuclei: Quasiparticlesand Phonons (Bristol, 1992) N. Tsoneva, H. Lenske, Ch. Stoyanov, Phys. Lett. B 586 (2004) 213 N. Tsoneva, H. Lenske, Phys. Rev. C 77 (2008) 024321 Nuclear Ground State Single-Particle States Phenomenological density functional approachbased on a fully microscopic self-consistent Skyrme Hartree-Fock-Bogoljubov (HFB) theory Pairing and Quasiparticle States Excited states deformations, vibrations, rotations HMph - multipole interaction in the particle-hole channel; HSMph - spin-multipole interaction in the particle-hole channel; HMpp - multipole interaction in the particle-particle channel isoscalar interaction isovector interaction N.Tsoneva, ERICE14

  6. Phenomenological Density Functional Approach for Nuclear Ground States P. Hohenberg, W. Kohn, Phys. Rev. 136 (1964) B864; W. Kohn, L. J. Sham, Phys. Rev. 140 (1965) A 1133. N. Tsoneva, H. Lenske, PRC 77 (2008) 024321 The total binding energy B(A) is expressed as an integral over an energy-density functional effective potential Z=50 rq, tq, kq– number, kinetic and pairing density neutron skin thickness N.Tsoneva, ERICE14

  7. The thickness of the neutron skin scaled with the difference of the Fermi levels of the protons and neutrons DeF corrected for the Coulomb barrier. Even-Even Neutron-Rich Nucleus E E Ec Vc(r)~Ze2/r 0 0 132Sn r eFn 124Sn DeF 116Sn eFp 108Sn 104Sn Neutrons Protons a measure of how loosely the neutrons are bound compared to the protons. S2p, S2n – two proton (neutron) separation energies, EC – the height of the Coulomb barrier at the nuclear radius (CCF=Coulomb Corrected Fermi energy) N.Tsoneva, ERICE14

  8. Calculations of Ground State Densities in Z=50, N=50,82 Nuclei Radius [fm] N. Tsoneva, H. Lenske, Phys. Rev. C 77 (2008) 024321 R. Schwengner et al., Phys. Rev. C 78 (2008) 064314 N.Tsoneva, ERICE14

  9. Theory of Nuclear Excitations Quasiparticle-Phonon Model: V. G. Soloviev: TheoryofAtomicNuclei: Quasiparticlesand Phonons (Bristol, 1992) The QPM basis is built of phonons: labels the number of the QRPA state The phonons are not ‘pure‘ bosons: Pauli principle fermionic corrections ~ QRPA equations are solved: N.Tsoneva, ERICE14

  10. Anharmonicities in Nuclear Wave Function Foreven-evennucleusthe QPMwavefunctionsare a mixtureofone-, two- andthree-phononcomponents one-phonon part two-phonon part three-phonon part M. Grinberg, Ch. Stoyanov, Nucl. Phys. A. 573 (1994) 231 N.Tsoneva, ERICE14

  11. Two-Phonon Quadrupole-Octupole 1-states U. Kneissl, N. Pietralla, and A. Zilges, J. Phys. G: Nucl.Part.Phys. 32, R217 (2006) stable and unstable Sn nuclei N. Tsoneva, H. Lenske, Ch. Stoyanov, Phys. Lett. B 586 (2004) 213 Excitationprobabilityofthe 21+statefromthegroundstate Excitationprobabilityofthe 31-statefromthegroundstate Excitationprobabilityofthe 11-statefromthegroundstate E1 transitionprobabilityofthe 31-statetothe 21+state N.Tsoneva, ERICE14

  12. Pygmy Dipole Resonance in Sn Isotopes N. Tsoneva, H. Lenske, PRC 77 (2008) 024321 GDR GDR GDR PDR PDR PDR N>Z N=Z Transition densities are related to nuclear transition strengths Radius [fm] N.Tsoneva, ERICE14

  13. Pygmy Dipole Resonance and the Dynamics of Nuclear Skin N. Tsoneva, H. Lenske, PRC 77 (2008) 024321 Neutron numberincreasing Neutron skinincreasing Aconnection between PDR strengths and neutron skins Similar observations found also in N=50, 82 isotones ! N.Tsoneva, CGS15

  14. Multiphonon Calculations of E1 Transitions in 112,120Sn submitted to PRC N/Z(112Sn)= 1.24 N/Z(120Sn)= 1.4 PDR PDR GDR (E*>8MeV) (1ph) PDR (1ph+2ph+3ph) N.Tsoneva, ERICE14

  15. Dynamics of Neutron Skin Oscillations in N=50 Isotones exp: R. Schwengner et al., First systematic photon-scattering experiments in N=50 nuclei: using bremsstrahlung produced with electron beams at the linear accelerator ELBE, Rossendorf and quasi-monoenergetic g – rays at HIgS facility, Duke university. N.Tsoneva, ERICE14

  16. Total cross section of 85Krg (n,g)86Kr reaction R. Raut,…,N.Tsoneva et al., Phys. Rev. Lett. 111, 112501 (2013). A way to investigate 85Kr branching point and the s-process:85Kr ( t ~ 10.57 Y) ground state is a branching point and thus a bridge for the production of 86Kr at low neutron densities. QRPA, QPM calculations by N. Tsoneva TALYS calculations by S. Goriely N.Tsoneva, ERICE14

  17. Population of 86Kr in n-capture reactions related to s- and r-processes of the nucleosynthesis s-process r-process TALYS calculations by S. Goriely N.Tsoneva, ERICE14

  18. Theoretical Prediction of Pygmy Quadrupole Resonance N. Tsoneva, H. Lenske, Phys. Lett. B 695 (2011) 174 PQR strength increases with the neutron number: B(E2) ~ 1/ enb2 PQR – pygmy quadrupole resonance ISGQR – isoscalar giant quadrupole resonance IVGQR – isovector giant quadrupole resonance ISGQR ISGQR PQR PQR IVGQR I=0 ISGQR I=1 I=0 ISGQR ISGQR PQR ISGQR PQR IVGQR I=0 I=1 ISGQR ISGQR PQR PQR IVGQR I=0 ISGQR I=1 N.Tsoneva, ERICE14

  19. QPM calculations in comparison with data M. Spieker, J. Endres, A. Zilges, Universität zu Köln (g,g‘) N.Tsoneva, CGS15

  20. Parity Measurements with Polarized Photon Beams of Low-energy Dipole Excitations at HIgS, Duke University A. Tonchev…N. Tsoneva, et al., Phys. Rev. Lett. 104, 072501 (2010) 138Ba sgg(M1)/sgg(E1) ~ 3% • First systematic spin and paritymeasurements in comparison • with QPM calculations: • 138Ba verified for the first time that the pygmy dipole resonance is predominantly electric dipole in nature. • The fine structure of the M1 spin-flip mode is explained. • Separation of the PDR to isoscalar and isovector. Interplay between the GDR and the PDR at higher energies. N.Tsoneva, CGS15

  21. Fine Structure of the Giant M1 Resonance in 90Zr Precision data on M1 strength distributions are of fundamental importance Spin and Parity Determination at HIgS, Duke University, USA G. Rusev, N. Tsoneva, F. Dönau, S. Frauendorf, R. Schwengner, A. P. Tonchev, A. S. Adekola, S. L. Hammond, J. H. Kelley, E. Kwan, H. Lenske, W. Tornow, and A. Wagner, Phys. Rev. Lett. 110, 022503 (2013). gseff=0.8 gsbare • Explaining the fragmentation pattern and the dynamics of the ‘quenching’. • Multi-particle multi-hole effects increase strongly the orbital part of the magnetic moment. • Prediction of M1 strength at and above the neutron threshold. SB(M1)Exp. = 4.5 (6) mN2 SB(M1)QPM. = 4.6 mN2 Ec.m.Exp. = 9.0 MeV Ec.m.QPM = 9.1 MeV N.Tsoneva, ERICE14

  22. Conclusions Thank you ! • A theoretical method based on Density Functional Theory and Quasiparticle-Phonon Model is developed. Presently, this is the only existing method allowing for sufficiently large configuration space such that a unified description of low-energy single-particle, multiple-phonon states and the giant resonances is feasible. • Different applications of the method are presented: - systematic studies of low energy dipole strengths reveal new mode of nuclear excitation - Pygmy Dipole Resonance as a unique mode of excitation correlated with the size of the neutron skin. - theoretical prediction of a higher order multipole pygmy resonance – Pygmy Quadrupole Resonance. - description of the fragmentation pattern of E1, E2 and M1 strengths - nuclear structure input for astrophysics N.Tsoneva, ERICE14

  23. First Systematic Studies of the PDR in N=50 Isotones Experiment: bremsstrahlung produced with electron beams at the linear accelerator ELBE and quasi-monoenergetic g – rays at HIgS facility at Duke university. R. Schwengner,…, N.Tsoneva et al, Phys. Rev. C 87, 024306 (2013) N.Tsoneva, LANZHOU14

  24. Cross-Section measurements of the 86Kr(g,n) Reaction to Probe the S-Process Branching at 85Kr R. Schwengner… N. Tsoneva et al., Phys. Rev. C 87, 024306 (2013); R. Raut…N. Tsoneva et al., Phys. Rev. Lett. 111, 112501 (2013). (g,g‘) data 86Kr QRPA 86Kr Lorentz strength function N.Tsoneva, LANZHOU14

  25. QRPA CALCULATIONS OF PQR STATES IN SN ISOTOPES N. Tsonevaand H. Lenske, Phys. Lett. B 695 (2011) 174 Pygmy Quadrupole Resonance is a genuine mode B(E2) increases with the neutron number N B(M1; 2i+ 21+) ~ 10-2mN2 B(E2) ~ 1/ enb2 g9/2 - a proton Fermi level; epb= -12.88 MeV in 134Sn ; epb=-7.20 MeV in 104Sn N.Tsoneva, CGS15

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