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Spectroscopy of Hard-to-Reach Nuclei with Deep-Inelastic Heavy-Ion Reactions

Research group from the Niewodniczanski Institute of Nuclear Physics PAN-KRAKOW is collaborating with INFN LNL Legnaro Tandem and ALPI Linac GASP, PRISMA-CLARA spectrometer to study neutron-rich nuclei produced in deep-inelastic processes. This research focuses on the evolution of nuclear structure, shell model configurations, and identification of excited states in odd K isotopes.

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Spectroscopy of Hard-to-Reach Nuclei with Deep-Inelastic Heavy-Ion Reactions

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  1. Research group: R.Broda, B.Fornal, W.Królas, T.Pawłat, J.Wrzesiński H.Niewodniczanski Institut of Nuclear Physics PAN-KRAKOW Collaboration with the INFN LNL Legnaro Tandem and ALPI Linac GASP, PRISMA-CLARA spectrometer Spectroscopy of hard-to-reach nuclei with deep-inelastic heavy-ion reactions

  2. Neutron-rich nuclei produced in deep-inelastic processes • Beams of heavy-ions at energies above the Coulomb barrier • Transfer of nucleons – trend to equilize N/Z ratio • Population of Yrast states in final fragments

  3. Thick target experiments • Fragments stopped in the target, no isotopic identification • Aquisition of high statistics g-g coincidence data sets • Level structure from coincidence analysis, ID from cross-coincidences and/or known transitions GAMMASPHERE 4 R. Broda et al., JPG 32, 151 (2006) 4 W. Królas et al., NPA 724, 289 (2003)

  4. 66Ni 48Ca (330 MeV) + 238U (thick target) GAMMASPHERE at Argonne 48Ca

  5. GASP at LEGNARO 64Ni (275 MeV) + 130Te (thick target) 130Te 64Ni

  6. 1.26 1.10 70Ni42 72Ni44 R.Broda et al., Phys.Rev. Lett. 74, 868 (95) - 5- 4+ (4+, 3-) (5-) 2+ 1114 (2+) 0+

  7. 8 g-ray thick target measurements with DIC advantages limitations Gamma spectra very complicated (hundreds of sources) Gamma rays from the short lived states smeared out by the Doppler effect (emitted before a product is stopped) Difficulties of identifications without a starting point. Angular distribution of g rays almost isotropic and ~ limitations ~ advantages PRISMA CLARA GASP Gamma rays from all reaction products Gamma rays from the stopped nuclei – narrow lines – easy analysis ofg-g coincidences Detection of cross-coincidences – some potential for identification

  8. PRISMA spectrometer • A magnetic heavy ion spectrometer designed to fully identify (A, Z)fragments deflected at large angles • CLARA: an array of 24 Clover detectors 238U + 330 MeV 48Ca • Complementary sets of data: PRISMA – (A,Z) identification, fast g transitionsand GAMMASPHERE – g-g coincidence data

  9. f5/2 p1/2

  10. 2+

  11. Evolution of Nuclear Structure with the Increase of Neutron Richness • Changes in shell structure – rearrangements of orbitals • Vanishing of shell gaps, appearance of new „magic numbers” • Experimental evidence needed • Experimental challenge – nuclei not easily accessible

  12. Shell model description of neutron-rich Potassium isotopes • For Potassium (Z=19): a proton-hole, nearest shells are ps1/2, pd3/2and pd5/2 • For neutron-rich (N > 28): neutrons in np3/2, np1/2 and/or nf5/2 shells 48Ca double closed-shell configuration

  13. Evidence of a 7/2– isomer in 47K 7/2– isomer, T1/2 = 7 ns 1660 M2 3/2+ 1/2+ 1660 keV line not in prompt gamma spectrum, assigned as an M2 isomeric transition: 7/2– 3/2+

  14. 7ns M2

  15. πf7/2 πf7/2 υp3/2 3+ 4+ 2+ + νp3/2 5+ πd3/2–1υp3/2 πd3/2–1 0– 3– πs1/2–1 1– πs1/2 –1υp3/2 2– 47K28 2– 1– 48K29 Shell model configurations in 48K

  16. PRISMA GAMMASPHERE First experimental identification of excited states in 48K • Identification of 48K gamma lines from PRISMA • Level scheme established from GAMMASPHERE coincidence data • New 6.5 ns isomer placed in 48K

  17. πf7/2 υp3/2 π-2 πd3/2 υp3/2 πs1/2 υp3/2

  18. πf7/2 πd3/2–1 πs1/2–1 First observation of excited states in 49K • Gamma lines identified from PRISMA • Level scheme from coincidence analysis PRISMA

  19. MeV 2 1 0 2814 2522 2107 7/2– 2020 1294 1081 excitation energy 738 771 980 3/2+ 474 360 561 1/2+ 41K22 39K20 43K24 45K26 49K30 47K28 Energies of lowest 1/2+, 3/2+and7/2–states in odd K isotopes

  20. 24 26 N=20 22 28 30 1 0 -1 -2 -3 πs1/2–1 MeV πd3/2–1 Evolution of relative πs1/2–1andπd3/2–1 proton single particle energies • As neutrons occupy the nf7/2 orbital, proton orbitals are shifted –interaction nf7/2↔pd3/2 is attractive, nf7/2↔ps1/2 is repulsive • This behaviour consistent with the predicted monopole effect of the tensor force

  21. Kraków group and collaborators R. Broda, B. Fornal, W. Królas, T. Pawłat, J. Wrzesiński IFJ PAN Kraków S. Lunardi, A. Gadea, N. Marginean, L. Corradi, A.M. Stefanini, F. Scarlassara, G. Montagnoli, M. Trotta, D. Napoli, E. Farnea Laboratori Nazionali di Legnaro and INFN Padova R.V.F. Janssens, M.P. Carpenter, T. Lauritsen, D. Seweryniak, S. Zhu Argonne National Laboratory

  22. 3- 449 2- 279 1- 3+ 2+ 4+ πf7/2 2020 5+ + νp3/2 0- 3- 1- 360 πd3/2 2- 2- 0 πs1/2 1- 47K28 48K29

  23. New experimental opening • Thick target data insufficient:difficult isotopic identification,fast gamma transitions unobserved • PRISMA spectrometer designed for identification of deep-inelastic reaction fragments PRISMA

  24. πf7/2 υp3/2 (5+) 6.5ns πd3/2–1υp3/2 (3–) (1–) πs1/2 –1υp3/2 New excited states and their configuration assignment in 48K

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