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Paddy Regan Dept. of Physics University of Surrey, UK E-mail: p.regan@surrey.ac.uk

Deep-Inelastic and Multinucleon Reactions with Discrete Gamma - ray Spectroscopy: A Brief Review. Paddy Regan Dept. of Physics University of Surrey, UK E-mail: p.regan@surrey.ac.uk. Physics of neutron-rich nuclei is the evolution of shell structure related

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Paddy Regan Dept. of Physics University of Surrey, UK E-mail: p.regan@surrey.ac.uk

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  1. Deep-Inelastic and Multinucleon Reactions with Discrete Gamma-ray Spectroscopy: A Brief Review Paddy Regan Dept. of Physics University of Surrey, UK E-mail: p.regan@surrey.ac.uk

  2. Physics of neutron-rich nuclei is the evolution of shell structure related • to large energy gaps in the nuclear single-particle spectrum. • Reasons to study neutron-rich nuclei include: • Evolution of collective modes (vibrations, rotations, superdef ?) • from spherical states by altering position in (N, Z, Ip, Ex) space. • Identification of specific orbitals, e.g. via isomers; g-factors; • B(E2:I->I-2); shell model, seniority, Nilsson schemes etc. • 3) Identifying new nuclear ‘exotica’, e.g., b-/proton/a-decaying states; • new symmetries (e.g., a32), shell closures, shape changes..etc.

  3. (Some) DIC basics. • Thick or thin targets ? (Ip , Ex,N, Z) ; isomer gating etc. • Thin target multi-nucleon transfer reactions: • Neutron-rich C nuclei (Berlin BRS). • N~20, Island of Inversion. • N=32,34 (sub)-shell closures, Se (Z=34, N=50). • 48Ca magic number(s). • N=50 robustness and shell closure. • Rotation/vibration evolution in A~100. • 132Sn region • Seniority Ip=10+ isomers, h11/2 neutron hole migration ? • Surface diffuseness, weakening of N=82 shell ? • A~170-190 K-isomerism and nuclear shape symmetry. • 208Pb at high spins; octupole collective vibrations etc. • U, Th octupole states, (very) high-j intruders (k17/2 etc.) • DIC with RIBs (24Ne beam at GANIL) • TIARA (d,p) etc. in inverse kinematics….

  4. Courtesy, Bogdan Fornal

  5. Courtesy, Bogdan Fornal

  6. R.Broda et al., Phys. Rev. C49 (1994)

  7. 208Pb 64Ni W. Krolas et al., Nucl. Phys. A724,289 (2003).

  8. Advantages and limitations of g-ray thick target measurements with DIC 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 ADVANTAGES 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

  9. Deep-inelastic reactions For K-Isomers with 238U beams 3.5 MeV, >3 ms, 16+ 186W • 238U at 1600 MeV • 186W (16 mg cm-2) • μs →ms beam pulsing • Argonne/Notre-Dame • array of 12 Ge dets. 1.5 MeV, 18 μs, 7– Off-beam singles, 7h Out-of-beam condition yields only lines from the new isomers. Total singles, 15 min. Without an off-beam timing condition, only Coulomb excitation lines are seen. Courtesy, Carl Wheldon

  10. z x q1 q2 f1 f2 y

  11. Ge TLF beam qtlf,ftlf qblf,fblf BLF M . Simon et al., Nucl. Inst. Meth. A452, 205 (2000) Rochester Group TOF ~5-10 ns. ns-ms isomers can de-excite in be stopped byCHICO position detector. Delayed gs can still be viewed by GAMMASPHERE.

  12. 100Mo + 136Xe @ 700 MeV GAMMASPHERE + CHICO PHR, A.D. Yamamoto et al., AIP Conf. Proc. 701 (2004) p329

  13. PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313 Can see clearly to spins of 20ħ using thin-target technique.

  14. nano to microsecond isomer tagging ?

  15. Isomer gating very useful in DIC experiments. PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313

  16. A.D.Yamamoto, Surrey PhD thesis (2004) Wilczynski (‘Q-value loss) Plot

  17. Can we use the data from the CHICO+Gammasphere expt. to understand the ‘DIC’ reaction mechanism ? A wide range of spins & nuclei are observed.

  18. What about the spin input ?

  19. R. Bock et al., Nukleonika 22 (1977) 529

  20. Fold distributions highlight different reaction mechanisms +2p -2n +2n PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313

  21. BLFs TLFs elastics PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313

  22. Emission angle of TLFs can give information/selection on reaction mechanism (and spin input).

  23. 198Pt +136Xe, 850 MeV J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) 024316

  24. Temporal separation can clearly identify ‘prompts’ and isomer decays 136Xe + 198Pt J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) 024316

  25. J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) 024316 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 84 83 82 81 80 79 78 77 nano and microsecond isomers on gated 198Pt+136Xe with GAMMASPHERE+CHICO DIC 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 76 75 74 73 59 58 57 56 55 54 53 52 51 50 N/Z compound

  26. J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313 136Xe+198Pt Target-like fragment isomers 184W 195Os 192Pt 185Re 191Os 198Pt 193Au 192Os

  27. g-g information and lifetime determination of 195Os isomer decay

  28. Dobon, Wheldon, Regan et al., New isomer in 195Os identified in GSI projectile fragmentation confirmed ‘in-beam’ CHICO+GAMMASPHERE g-g data. M.Caamano, P.M.Walker, PHR et al., Eur. Phys. J. A (2005)

  29. 136Xe+198Pt reaction beam-like fragment isomers. 132Xe 128Te 130Te 136Xe 138Ba 131I 137La 133I J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313

  30. J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) 024316 10+ N=80 isotone

  31. N=80 isotonic chain, 10+ isomers, (nh11/2)-2I=10+ Q. Why does Ex(10+) increase while E(2+) decreases ? 91(2) ns

  32. Energy of N=80 Ip=10+ isomers correlates with energy increase of 11/2- single neutron hole in N=81 isotones. Increase in 10+ energy, plus expansion of proton valence space means 8+ yrast state now (mostly) NOT (nh11/2)-2 for Z>54 Ex, Ip=11/2 - N=81 Ex, Ip=10 N=80 Valiente-Dobon, PHR, Wheldon et al., PR C69 (2004) 024313

  33. Pair Truncated Shell Model Calculations (by Yoshinaga, Higashiyama et al. Saitama) predict yrast 8+ in 136Ba no longer mostly (nh11/2)-2 but rather, (pd5/2)2(pg7/2)2

  34. BRS+EUROBALL • 18O at 90 MeV on 9Be (98 μg.cm-2) • BRS: q = ±12.5° → ±45.5° • Euroball: 15 clusters, 26 clovers (209 crystals) • Unique-Z id., position to 1 mm, energy of recoil • Particle-γ, particle-γ-γ and particle-particle-γ-γ • coincidences Doppler correction from energy in BRS Add-back included Z Carbon gate Energy Courtesy, Tzany Kokolova

  35. CLARA S. Lunardi, Acta. Phys. Pol. B36 (2005) 1301

  36. S. Lunardi, Acta. Phys. Pol. B36 (2005) 1301 A. Gadea et al., J. Phys. G (2005) in press

  37. S. Lunardi, Acta. Phys. Pol. B36 (2005) 1301

  38. Mg Na Ne 24Ne F O N C B Be Li He H Report of the E421S experiment (spokeperson F.Azaiez): aim of the experiment DIC with RIBs! A new era ? Deep Inelastic Collision reaction with light exotic beam Population of exotic Ne-F-O isotopes • cross section measurements • g spectroscopy Ne-O-F courtesy, Giovanna Benzoni

  39. Report of the E421S experiment: Experimental details • reaction: 24Ne @ 7.923 MeV/A + 208Pb (10.9 mg/cm2) • 24Ne5+ , Ibeam ~ 1.5 . 105 pps • beam on target for 7 days • setup: Vamos + EXOGAM • Vamos @ 45° • EXOGAM 11 detectors • (2 without Compton shield) • Typical count rates: • Ions: 30/min  Total Ion counts: 7*24*60*30 = 302400 •  cross section determination is feasible • Ion-gamma coincidence 70/h • Total Ion-gamma coinc. 7*24*70 = 11760 • only spectroscopy of inelastic ch. courtesy, Giovanna Benzoni

  40. ID-plot E E (a.u.) F Ne O Na DE (a.u) Report of the E421S experiment: very preliminary spectra 3 days of statistics (~ 1/2) Working on mass separation courtesy, Giovanna Benzoni Analysis in progress • Conditions: • Si-gamma coincidence • Prompt gamma peaks • calculated v/c Ne (inelastic)

  41. 23F ~ 20 mb (1p removal) 24Ne ~ 500 mb 26Ne ~ 80 mb (2n pick up) F Ne Beam intensity required to study weaker channels • to get to more exotic Ne isotopes  ~ 106 • to get to F  5.106 • to get to O  ~ 107 Report of the E421S experiment: future courtesy, Giovanna Benzoni

  42. TIARA courtesy, Wilton Catford

  43. TIARA Experimental Results for 24Ne(d,p)25Ne Transfer with TIARA 10 MeV/u (d,p) 25Ne Courtesy, Wilton Catford

  44. DIC physics…. • Neutron-rich C nuclei (Berlin BRS). • N~20, Island of Inversion. • N=32,34 (sub)-shell closures, Se (Z=34, N=50). • 48Ca magic number(s). • N=50 robustness and shell closure. • Rotation/vibration evolution in A~100. • 132Sn region • Seniority Ip=10+ isomers, h11/2 neutron hole migration ? • Surface diffuseness, weakening of N=82 shell ? • A~170-190 K-isomerism and nuclear shape symmetry. • 208Pb at high spins; octupole collective vibrations etc. • U, Th octupole states, (very) high-j intruders (k17/2 etc.) • DIC with RIBs (24Ne beam at GANIL) • TIARA (d,p) etc. in inverse kinematics….

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