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Recent Nuclear Structure and Reaction Dynamics Studies Using Mutlinucleon Transfer Reactions

Recent Nuclear Structure and Reaction Dynamics Studies Using Mutlinucleon Transfer Reactions. Paddy Regan Dept. of Physics University of Surrey,UK E-mail: p.regan@surrey.ac.uk. Laser Physics Letters 1 (2004) 317-324. Outline of Talk. Thin target multinucleon transfer reactions:

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Recent Nuclear Structure and Reaction Dynamics Studies Using Mutlinucleon Transfer Reactions

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  1. Recent Nuclear Structure and Reaction Dynamics Studies Using Mutlinucleon Transfer Reactions Paddy Regan Dept. of Physics University of Surrey,UK E-mail: p.regan@surrey.ac.uk

  2. Laser Physics Letters 1 (2004) 317-324

  3. Outline of Talk • Thin target multinucleon transfer reactions: • 100Mo+136Xe : alignments, E-GOS plots and some reaction mechanism info. • 198Pt+136Xe: 136Ba Ip=10+seniority isomers, effective charges and some reaction mechanisms • 184W K-isomers and –4p transfer • Future Aims/ Plans. • 170Dy (ish) • N=50 (ish)

  4. Main physics interest in neutron-rich nuclei is based on the • EVOLUTION OF SHELL STRUCTURE and the appearance of • ‘large gaps in the nuclear single-particle spectrum’. • Reasons to study neutron-rich nuclei • Evolution of collective modes (vibrations, rotations, superdef ?) • from spherical states by altering (N,Z,Ip, Ex). • 2) Identification of specific nucleonic orbitals, e.g. via isomeric • decays, g-factors, B(E2:I->I-2), effective charges, shell model • descriptions, seniority schemes, deformed (Nilsson) schemes etc. • 3) Identifying new nuclear ‘exotica’, e.g., the unexpected, • beta-decaying high-spin states, new symmetries (e.g., a32), • neutron ‘skins’, new shell closures, shape changes etc.

  5. See eg. Broda et al. Phys. Rev Lett. 74 (1995) p868 Juutinen et al. Phys. Lett. 386B (1996) p80 Wheldon et al. Phys. Lett. 425B (1998) p239 Cocks et al. J. Phys. G26 (2000) p23 Krolas et al. Acta. Phys. Pol. B27 (1996) p493 Asztalos et al. Phys. Rev. C60(1999) 044307 Aim? To perform high-spin physics in stable and neutron rich nuclei. Problem: Fusion makes proton-rich nuclei. Solutions? (a)fragmentation (b) binary collisions/multi-nucleon transfer Modified from Introductory Nuclear Physics, Hodgson, Gadioli and Gadioli Erba, Oxford Press (2000) p509

  6. z x q1 q2 f1 f2 y

  7. Ge TLF beam qtlf,ftlf qblf,fblf BLF 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.

  8. 100Mo + 136Xe @ 700 MeV GAMMASPHERE + CHICO PHR, A.D. Yamamoto et al., AIP Conf. Proc. 701 (2004) p329

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

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

  11. Crossing and alignments well reproduced by CSM, although AHVs

  12. PHR, Beausang, Zamfir, Casten, Zhang et al., Phys. Rev. Lett. 90 (2003) 152502

  13. E-GOS plot appears to indicate that Vibrator-Rotator phase change is a feature of near stable (green) A~100 nuclei. BUT….what is the microscopic basis ? ‘Rotational alignment’ can be a crossing between quasi-vibrational GSB & deformed rotational sequence. (stiffening of potential by population of high-j, equatorial (h11/2) orbitals). PHR, Beausang, Zamfir, Casten, Zhang et al., Phys. Rev. Lett. 90 (2003) 152502

  14. 82 1h11/2 50 [550]1/2- 1g9/2 [541]3/2-

  15. What about odd-A nuclei….are the nh11/2 bands ‘rotational’ ?

  16. See PHR, Yamamoto, Beausang, Zamfir, Casten, Zhang et al., AIP Conf. Proc. 656 (2002) p422 ‘Weak Coupling’ Eg/(I-j) E-GOS extension for odd-A Suggests 11/2- band is anharmonic, g-soft rotor? BUT seems to work ok for +ve parity bands vib ->rotor following (nh11/2)2 crossing.

  17. Carl Wheldon (HMI-Berlin) has suggested extension of E-GOS by ‘renormalising’ the rotational energies at the bandhead. If the band-head spin of a sequence is given by j then substituting I-j in place of I, one obtains,

  18. Even-Even yrast sequences and odd-A +ve parity only show rotational behaviour after (nh11/2 )2 crossing…. seems to work ok, nh11/2 bands now look like rotors,

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

  20. Kinematics and angular mom. input calcs (assumes ‘rolling mode’) for 136Xe beam on 100Mo target. Estimate ~ 25hbar in TLF for ~25% above Coul. barrier. For Eb(136Xe)~750 MeV, in lab qblf~30o and qtlf~50o. 100Mo +136Xe (beam) DIC calcs.

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

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

  23. Emission angle of TLFs can give information/selection on reaction mechanism (and maybe spins input ?)

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

  25. Gating on angle gives a dramatic channel selection in terms of population. Relative Intensities of 6+->4+ yrast transitions in TLFs (relative to 100Mo) for 136Xe beam on 100Mo target at GAMMASPHERE + CHICO.

  26. 198Pt +136Xe, 850 MeV J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) 024316

  27. 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

  28. 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

  29. 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

  30. PHR, Valiente-Dobon, Wheldon et al., Laser Phys Letts. 1 (2004) 317

  31. Can see 184-194Os in binary partner channels. i.e.in 2p transfer, up to 14 neutrons evaporated. ( 4n -> 194Os is heaviest known).

  32. J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313 198Pt, 2+ 136Xe, 2+

  33. J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313 138Ce 125Sb

  34. Identification of new ‘seniority’ isomer in 136Ba, N=80 isotone. T1/2=91(2) ns J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) 024316

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

  36. Structure of 8+ final state changes from 134Xe -> 136Ba ? See Valiente-Dobon, PHR, Wheldon et al., PRC69 (2004) 024313 Isomer decay also depends on structure of final state N=80, (nh11/2)-210+ isomers

  37. Energy of N=80 Ip=10+ isomers correlates with energy increase of 11/2- single neutron 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

  38. Valiente-Dobon, PHR, Wheldon et al., PRC69 (2004) 024313

  39. 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

  40. Expect neutron ‘seniority scheme’ for (nh11/2)-2 ‘j2’ mutliplet configuration at N=80 (e.g. 130Sn). 132Te, 134Xe have proton excitations due to g7/2, d5/2 at 0+,2+,4+,6+ but not competing 8ħ and 10ħ states. Extra collectivity for higher-Z pushes down 0+ and 2+. Proton s.p. energies used in 136Ba SM calcs h11/2 2.760 Protons, max. seniority 2 spin = 6 ħ (from (pg7/2)2. Seniority 4 states though can have up to 7/2 + 5/2 + 5/2 +3/2 = 10 ħ d5/2 0.963 g7/2 0.000

  41. low-K mid-K high-K j K Search for long (>100ms) K-isomers in neutron-rich(ish) A~180 nuclei. Walker and Dracoulis Nature 399 (1999) p35 (Stable beam) fusion limit makes high-K in neutron rich hard to synthesise N=104 also a good number for K-isomers.

  42. 170Dy, double mid-shell, ‘purest’ K-isomer ? (see PHR, Oi, Walker, Stevenson and Rath, Phys. Rev. C65 (2002) 037302) Kp=6+state favoured Max at 170Dy

  43. Best K-isomer? Doubly-mid-shell nucleus, 170Dy N=104, Z=66 (Np.Nn=352=Maximum!). Appears to be a correlation between fn values and NpNn for K=6+ isomers in A~180 region. (see PHR, Oi, Walker, Stevenson & Rath, Phys. Rev. C65 (2002) 037302) Extrapolation suggests isomer in 170Dy lives for hours….could be beta-decay candidate. 170Dy ? N=104 isotones, K=6+ energy 172Hf, 174Yb, 174Hf, 176Hf, 178Hf, 178W K=6+ isomers Try at PRISMA in 2005

  44. International Conference On NUclear STructure, Astrophysics & Reactions University of Surrey, Guildford, UK5-8 January 2005 Payment deadline last Friday (1st October) http://www.ph.surrey.ac.uk/cnrp/nustar05

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