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Nuclear structure probed by precision atomic mass measurements in a Penning trap

This article explores the use of precision atomic mass measurements in a Penning trap to probe the structure of the nucleus. It discusses the applications of weak interaction studies, fundamental physics, and nuclear astrophysics. It also highlights the capabilities of the JYFLTRAP setup and the Ion Guide ISOL system for accurate mass measurements of short-lived and rare isotopes. The article emphasizes the importance of experimental data in informing mass predictions and nuclear structure theories.

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Nuclear structure probed by precision atomic mass measurements in a Penning trap

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  1. Nuclear structure probed by precision atomic mass measurements in a Penning trap Ari Jokinen Department of Physics University of Jyväskylä

  2. (Short) introduction M(Z,N) = Mmn + Zmp + B(Z,N) contains all information of the structure of the nucleus Weak interaction studies and fundamental physics: (0+0+, n-physics, bb, part.-antipart., …) Sub-keV precision of less exotic nuclei: Data from dedicated experiments with stable isotopes and reaction Q-values Nuclear structure and nuclear astrophysics: Atomic masses of exotic isotopes with 1-100 keV precision: Usually based on the decay studies (Qa, Qb, …), extrapolations and interpolations (AME) and mass predictions

  3. Penning trap (and storage ring) era Access to Direct mass measurements of short-lived and rare isotopes with improved precision ! ATOMIC MASSES for nuclear physics: - benchmark mass predictions and nuclear structure theories - input for improved predictions far from stability BINDING ENERGIES and their DIFFERENCES over long chains of isotopes provide experimental information and verification: - evolution of nuclear structure - evolution shell gaps - pairing correlations - …

  4. 3) Spectroscopic information: Access to complementary information of nuclear structure vie decay spectroscopy and collinear laser spectroscopy 4) JYFLTRAP: Combination of RFQ cooler.buncher and Tandem Penning trap located in 7T superconducting solenoid: - M/DM purification 1-2 x 105 - Precision mass measurement applying TOF - Few keV precision for NS studies - 8 x 10-9 precision for QEC - 62Ga, T1/2=116ms, +/- 540 eV, 1.8 x 10-8 3 2 3 2) Ion Guide ISOL: LI-IG, HI-IG, fission IG Chemically inselective Fast (ms-regime) 1+ DC-beam at 30 keV with M/DM ~300 4 3 JYFLTRAP setup at IGISOL MASS MEASUREMENTS WITH JYFLTRAP 1) K130 accelerator: Ip ~ 50 mA and Ep ~ 20-70 MeV) HI-ions up to 132Xe (~5 MeV/u) Plenty of on-line time (K130 beam-on-target 7000 h/year) 1

  5. A. Kankainen et al., EPJA 29 (2006) 271 U. Hager et al., NPA 793 ( 2007) 20 Critical survey of AME and previous data; Nb

  6. JYFLTRAP data vs. AME 2003 N-def. A~100 0+0+ N-rich A~100

  7. Mass predictions vs. JYFLTRAP data U. Hager et al., NPA 793 ( 2007) 20 1. Tendency: Mass predictions and AME deviate from new precise data, but they often agree with each other !  Are predictions guided (too much) by AME ? 2. Plenty of new data and more is coming, but AME update will take years  model benchmarking and adjustment should be based on the experimental data !

  8. 20 40 60 80 0 Binding energies in transitional region A~100 Shape changes Shell gaps and sub-shell closures Quadrupole deformation b2 of even-even nuclei HFB + THO + LN M.V. Stoitsov et al., Phys. Rev. C 68 (2003) 054312 b2 < -0.2 -0.2 - -0.1 -0.1 - +0.1 -0.1 - +0.2 +0.2 - +0.3 +0.3 - +0.4 > + 0.4

  9. Two-neutron separation energies from Nito Pd

  10. Two-neutron separation energies from Tc to Pd

  11. Two-proton separation energies below 100Sn New data removes some of irregularities in the existing old data compiled in AME !  Liquid-drop behaviour

  12. Discontinuity at N~60, Z~40

  13. b2=0.4 b2=0.3 b2=0.0 Observed discontinuity appears in expected region of rapid changes of deformation and agrees perfectly with the recent collinear laser spectroscopy data Discontinuity at N~60, Z~40 – shape effect

  14. N=50 shell gap

  15. N=50 shell gap extracted from AME2003 ?

  16. N=50 shell gap from AME2003+Penning trap data

  17. Shell gap energies – predictions J.M. Pearson and S. Goriely, Nucl. Phys. A 777 (2006) 623-644 D2n(No) = S2n(No)-S2n(No+2) Z=28

  18. Dn = ¼(-1)A-Z+1[Sn(A+1,Z)-2Sn(A,Z)+Sn(A-1,Z)]c2 = ¼(-1)A-Z+1[-M(A+1,Z)+3M(A,Z)-3M(A-1,Z)+M(A-2,Z)]c2 Bohr-Mottelson Dn = 12/A1/2 [MeV], fixed Z Bohr-Mottelson Dn = 12/A1/2 [MeV], fixed A D.G. Madland and J.R. Nix, NPA476 (1988) 1 Dn = 5.7 exp(0.12I-8I2)/N1/3 [MeV] P. Vogel, B. Jonson and P.G. Hansen, PL 139B (1984) 227 Dn = (7.4-45I2)/A1/3 [MeV] Pairing OES of nuclear binding energies  pairing-gap energy in the standard BCS theory Differences measured masses  Dn or Dp G = strength of the pairing interaction en = single-particle energy l = chemical potential

  19. Pairing energies; close look as f(N) Dn = ¼(-1)A-Z+1[Sn(A+1,Z)-2Sn(A,Z)+Sn(A-1,Z)]c2 = ¼(-1)A-Z+1[-M(A+1,Z)+3M(A,Z)-3M(A-1,Z)+M(A-2,Z)]c2 Connection to: D in BCS-theory ? Pairing functional ???

  20. Indication of re-strengthening of Vnp – to be verified by further mass measurements ! P. Schury et al., PRC75 (2007) 055801 Proton-neutron pairing energies for o-o N=Z nuclei LEBIT, MSU (G. Bollen): Precise mass measurements of short-lived Ge, As and Se isotopes close to N=Z=33. Vanishing of Wigner energy while approaching 100Sn ?

  21. Summary and outlook • ISOLTRAP, JYFLTRAP, LEBIT, SHIPTRAP, CPT and TITAN: • 600 isotopes with keV-range precision and more to come … • ESR for the shortest half-lives and the most exotic cases with limited accuracy

  22. Precise direct masses of exotic isotopes: • Deficiencies in existing data set far from stability  Faults in AME compilation • Misguidance of atomic mass predictions and other models trying to reproduce AME mass surface Differences of atomic masses with keV-range accuracy: • Variations in two-particle separation energies reflects underlying nuclear structure • Evolution of shell gaps • Pairing gaps • Proton-neutron pairing energies • …

  23. Acknowledgements: V.-V. Elomaa T. Eronen U. Hager J. Hakala A. Jokinen A. Kankainen P. Karvonen T. Kessler I. Moore H. Penttilä S. Rahaman S. Rinta-Antila J. Rissanen J. Ronkainen A. Saastamoinen T. Sonoda C. Weber J. Äystö Department of Physics, P.O.Box 35 (YFL) FIN-40014 University of Jyväskylä

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