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Precision mass measurements of n-rich nuclei between N=50 and 82.

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## Precision mass measurements of n-rich nuclei between N=50 and 82.

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**Precisionmassmeasurements of n-richnucleibetween N=50 and**82. JuhaÄystöDepartment of Physics, University of Jyväskylä, Finland Helsinki Institute of Physics, Helsinki, Finland • Short overview on the experimental approach • Penning trap mass measurements on n-rich nuclei • Impact of improved knowledge of masses • Fine structure of mass surface vs. nuclear structure • two-neutron separation energies • odd-even staggering and pairing • Conclusions and outlook**Penningtrap**• Split ring electrode: • Dipolar RF • Quadrupolar RF • Coupling at nc • Homogenous B, quadrupolar V • Three eigenmotions • Axial (nz) • Magnetron (n- = 1 kHz) • Modified cyclotron (n+ =1 MHz) SIDEBAND MASS SPECTROMETRY:**JYFLTRAP @ IGISOL3fastuniversalmethod**• RFQ + 2 Penning traps • Isobaric/-meric cleaning • Mass measurements -fast, universal T. Eronen et al., Eur. Phys. J. A 48 (2012) 46**Beam purification**• Sideband cooling technique (G. Savard et al., Phys. Lett. A 158 (1991) 247) • R = M/DM up to 105**JYFLTRAP massmeasurements**SnSbTe rp, νp process 3. 132Sn region 58Ni 2. N≈60 subshell 0+→ 0+IMME mirror 1. N=50 shellclosure • Nuclear structure • Nuclear astrophysics (r process) • Fundamentalsymmetries ~0.1…20 keV precision (10-9…10-7)**Production in p-fissionrefs.: V. Rubchenya, J. Äystö,**Eur. Phys. J. A 48 (2012) 44H. Penttilä et al., Eur. Phys. J. A 48 (2012) 43 45Rh 60 62 64 66 68 70 72**Differencebetween 2003 mass data from the PT data**From a reviewby A. Kankainen, J. Äystö and A. Jokinen, J. Phys. G. submitted 2012. =(N-Z)/2**deformed N=60 region**JYFLTRAP TITAN; new ISOLTRAP**Neutron-rich masses close to 132Sn**J. Hakala, J. Dobaczewski et al., submitted to PRL (2012); arXiv:1203.0958 Isomers! (T1/2 > 100 ms) T1/2 ≈100 ms Agreement with ISOLTRAP data Is PERFECT! ISOLTRAP JYFLTRAP**Evolution of shellstructure at Z=50 and N=82**Two-protonshellgap for Z=50 Two-neutronshellgap for N=82 50 Shell gap 82**…theory vs. experiment ?**Correlationsareveryimportant !! M. Bender, G. F. Bertsch, and P.-H. Heenen. Global study of quadrupole correlation effects. Phys. Rev. C, 73 (2006) 034322 S. Goriely, N. Chamel, and J. M. Pearson Skyrme-Hartree-Fock-Bogoliubov nuclear mass formulas: Crossing the 0.6 Mev accuracy threshold with microscopically deduced pairing. Phys. Rev. Lett., 102 (2009)152503**Odd-evenstaggering (OES);a measure of empiricalpairinggap**3-point formula OES mostlydepends on the intensity of nucleonic pairing correlations in nucleibut is also affected by the polarisationeffects! OES(Nodd) measure of pairingeffects OES(Neven) impactedbysingle particlestatesaround Fermi level**Odd-evenstaggeringacross the N=82 shellclosure**J. Hakala, J. Dobaczewski et al., arXiv:1203.0958**Our QRPA calculationsreproduce the behavior seen in**experiment. We trace the cause to the difference in neutron pairing below and above N=82. Coulomb Excitation of Radioactive 132,134,136Te Beams and the Low BE2 of 136Te PHYSICAL REVIEW LETTERS 88 (2002) 222501 D. C. Radford,et al.**Sphericalself-consistentcalculationusing**Sly4 energydensityfunctional plus contactpairing Dobaczewski, Flocard, Treiner, Nucl. Phys. A 422(1984)103 Conclusion: The N=81-83 asymmetry in staggeringindicates - exclusion of pure surfacepairingforce - significantrole for polarizationeffects for Te and Xe!**1 mb**1 mb**Fall of 2012:**IGISOL and JYFLTRAP willoperate @ MCC30 & K130 cyclotrons Specialissue for IGISOL Science Laser hut Penningtraps RFQ-buncher**Summary**• Our knowledge of binding energies of neutron-rich nuclei has experienced a major revision during the last five years due to Penning-trap technique • Long isotopic chains from Ni to Pr , excluding iodine, measured at three Penning trap facilities: Jyvaskyla, CERN-ISOLDE and Argonne • Masses of over 300 nuclides produced in fission with uncertainties of 10 keV or less have become available. • The present data set provides: • A challenge for future development of mass models and theories • Higher sensitivity to reveal shape transitions and (sub)shell closures by mass differentials • A new tool to study odd-even staggering of binding energy as a probe for pairing effects in n-rich nuclei (in particular close to drip-line!)**Thank you for your attention!**…and T. Eronen, A. Kankainen, A. Jokinen and colleagues at**masses vs. twodifferentr-processpaths**P.A. Seeger, W.A. Fowler, and D.D. Clayton. Nucleosynthesis of heavy elements by neutron Capture, Astrophys. J. Suppl. Ser., 11:121, 1965. V. Bouquelle, N. Cerf, M. Arnould, T. Tachibana, and S. Goriely. Single and multi-event canonical r-process, Astron. Astrophys., 305:1005, jan 1996.**Ion Guide**(Light ion induced fusion) Ions. Atoms too,but they’re lost.**Continuous RF excitation**200 ms 131In states g.s: 9/2+, 280 ms 1/2-, 302(32) keV, 350 ms 21/2+, 3764(88) keV, 320 ms Purificationcycles + pulsed RF excitation 25-150-15 ms JYFLTRAP result: E*(1/2-)=365(8) keV To bepublishedby A. Kankainen et al. (1/2-)**Isomers can be separated (500 ms)**T. Eronen et al., NIM B 266 (2008) 4527 1.7 Hz, 233 keV/c2