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Decay Studies @ EURISOL

Detailed overview of decay mechanisms, exotic decays, and asymmetries in nuclear decay of exotic nuclei near the drip lines. Focus on short half-lives, high Qb values, and reduced transition probabilities.

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Decay Studies @ EURISOL

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  1. Decay Studies @ EURISOL María José García Borge Instituto de Estructura de la Materia, CSIC M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  2. Near the drip lines Overview Desintegration +-EC Desintegration - Desintegration  Fission • Halo structure • Disappearance of magic numbers • Exotic decays • Asymmtries • Order to Chaos M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  3. Short half-lives (ms) • High Qb values • Low Sp/n values • Selection rules: • Fermi: DT=0 ;DJ=0 ; pf = pi • Gamow-Teller: DT=0±1; DJ=0±1; pf = pi • Reduced transition probability: Decay properties of exotic nuclei • 1916Rutherford & Wood [Philos. Mag. 31 (1916) 379] • 1963Barton & Bell identified 25Si as p • Global properties -delayedparticle emission • + (C.E.) emission E,  Level density Spin, Isospin -decay properties M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  4. Production Methods • Short separation times (identification of very short T1/2 species) • Direct determination of B.R. • High detection efficiency(implantation of the source) • Simultaneous measurement of many nuclei • Pure beam • High magnetic resolving power • Full isotopic chain • Very good beam quality • Low energy  Point like sources M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  5. Super-conducting solenoid B=3.5 Tesla 33Ar p-spectrum free of -summing 0 2 3 4 Ep (MeV) State-of Art p spectrum ( = 4 keV) @ ISOL-Facilities • Study of the proton line shape • Physics beyond the SM (Björn’s Talk) • Isospin mixing in Fermi decays • Configuration mixing • Level interferences • Spin assignment • Excitation energies 32Ar Adelberger & García, Hyp. Int 129 (2000) 237 Bhattacharya & García in preparation 0 2.5 3.5 Ep (MeV) M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  6. Studies possible due to the development of the right target Development of Targets VC-target 32Ar CaO-target Equivalent setup And beam time ¡ Gain of a factor of 2400 in yield! M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  7. Counts Energy (keV) Strong beta summing Fragmentation Facility /Two solutions Bhattacharya & García in preparation MSU 32Ar JC Thomas et al., Eur Phys J A 21 (2004) 419 GANIL M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  8. Miernik, Pfützner et al. PRL99 (2007) 192501 Direct decay First Measurement of p-p correlation in 2p-radioactivity MSU 2002 T1/2 and E2p compatible with Sequential & direct decay PRC76 (2007) 041304R 70 % of the decay PRC72 (2005) 054315 M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  9. Transition from order to Chaos Middle Z  High Density Narrow States Fluctuations  Porter Thomas Distribution Low Z  Narrow States Direct structure information Very low Z  Broad States R-Matrix description: E,  M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  10. Beta delayed particle emitters Neutron Rich Nuclei • Halo structure • Disappearance of magic numbers B.Jonson & K. Riisager, NPA693 (2001) 77 M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  11. Number of Protons New Magic Number No Magic In discussion Number of Neutrons The Survival of Magic Numbers • The shell structure and the associated gaps are different far from stability. • Existence/survival of Magic Numbers depends on • The size of the gap • Structure of mean field near Fermi level (correlations np-nh • The disappearance of Magic Numbers was first observed in 31,32Mg. • In N=8, 11Li the gain in correlation is due to Pairing • In N=20 and N= 28 the gain in correlations 2p-2h is due to cuadrupole interaction. • The play of correlations can be so subtle that if one adds 2p to 32Mg we have the double magic nucleus 34Si. M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  12. Halo can affect beta decay in different ways; the spatial extension of the halo state reduces the overlap with the daughter states. Affect one transition or globally the BGT i.e. in the case of 11Li T1/2 and -B.R.  (P1/2)2 < 50 % The halo nucleons decay almost independently from the core, i.e. decay to the continuum: i. e. d Assuming halo state can be factorised (Nilsson et al, Hyp. Int 129 (2000) 67) βhalo state> = β(halo> core>) = (βhalo> ) core> + halo>(βcore>)  Similar decay pattern of the 2n-halo nucleus and its core -decay of halo nuclei M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  13. Even a neutron rich- nuclei emit charged particles 20.6 - 3/2- 1996 17.916 T1/2 = 8 ms 1983 9Li+d 1966 9Li 15.721 8Li+t 10.59 p 1980 d 8.82 8.982 1979 2+3n 7.315 9Be+2n 0.320 ½- 1974 Energías (MeV) g 0.504 0.320 ½+ 10Be+n 11Be 11Be Beta decay of an exotic nuclei M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  14. Anthony et al., PRC 65 (2002) 034310 b- 6He a+d M.J.G. Borge et al., Nucl. Phys. A560 (1993) 664 Zhukov et al., PRC47 (1993) 2937 βd-6He 10-4 11Li F.C. Baker, Phys. Lett. B 322 (1994) 17 6Li Intensity (decay-1 MeV-1) 10-5 D. Baye et al., Prog. Th. Phys. 91 (1994) 271 10-6 Exploring w.f.  10 fm 500 1000 0 0 Ed (keV) βd- spectrum of 6He Qd(Z,A) = 3.007 – S2n(MeV); 6He, 8He, 11Li, 14Be, 17B..etc M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  15. βd- spectrum of 11Li @ TRIUMF Raabe et al, PRL submitted • Implantation in a thin, highly segmented silicon detector • ISOL beams: intense, pure,good energy definition  control on the implantation • Full energy of ions is measured • High efficiency • Precise normalisation • Identification of channels through implantation-decay-decay correlationsin each pixel Decay to the continuum Favoured βd-11Li Zhukov PRC 52 (95)2461 Baye PRC79(06)064302 M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  16. 11Li Polarized radioactive beams: 11Li @ TRIUMF 8.8 8 3/2 7 6.179 3/2 11Be 5 5.958 2.6 MeV 3.4 MeV 10Be • Spin polarized 11Li beam • , n, n coincidences • Spin and parities of 7 levels in 11Be assigned. Hirayama, Phys. Lett. B 611 (2005)239 M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  17. ¿ Similar decay pattern of halo nuclei & core ? Factorisation holds for the 2n-halo 14Be and its core 12Be 14Be < 4 % to bound states Pn = 101  4 % Feeding to 1+ > 38 %; logft 3.5-4 P2n + 3P3n = 0.8  = 8 % Dufour et al., PLB206 (1988) 195 Belbot et al.,PRC56 (1997) 3038 Bergmann et al NPA658 (1999) 129 Can the halo state wave function of 11Li be factorised?  Study of the decay of 11Li and 9Li with emphasis in the highly excited states M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  18. 13.257 =0.45 5/2-  = 3.4(7) δ ≈ 3 5/2- δ=1.2±0.5 54.1(15)%  = 0.032(3) δ ≈ 0 PLB576 (2003)55 NP A692(2001)427 A = 9 isobar 3/2- (1/2,5/2)- (1/2)- 3/2- 3/2- Nyman et al., NPA 510 (1990) 189 Mikolas et al., PRC 37 (1988) 766 F. Ajzenberg-Selove, NPA 490 (1988) 1 M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  19. Charged particle emission in the 11Li-decay • Current knowledge: • Four decay channels • Two states in 11Be: 10.6 and 18.3 MeV. ? • Theory: SM predicts B(GT) strength distribution peaks between 15 and 20 MeV. • Experiment:  doppler broadening suggests significant (6%) feeding of states in this region. T. Suzuki and T. Otsuka, PRC 56(1997)847 H.O.U. Fynbo et al., NPA736 (2004)39 M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  20. Analysis techniques Energy & momentum conservation Momentum reconstruction Excitation energy of the 1-2 system: 11Li Beam 6He++n 60 g/cm2 • Deadlayer and carbon-foilenergy losses corrected • -background subtraction: • Efront- Eback  40 keV M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  21. Charged Particle Coincidences M. Langevin et al., NPA 366(1981) 449 127º - 180º D2 D4 ED2+ED4 M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  22. E11Be Q1 Q2 E’ 6He++n Evidence of decay through the 7He resonance 8.33 7.91 7He(gs) d  10 cm • Contribution of a new decay channel . • Contribution of a state at 16.3 MeV ( 1 MeV) ). In agreement with theoretical expectations and previous -experiment 2005 127º - 180º Preliminary 2007 d  8.5 cm M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  23. 7 x BC501 Liquid scintillator 15 cm x 30 cm Ge 1.2m 2m g 3m • Gamma detection • 3 Glover (4xHPGe) Universal set-up for spectroscopy studies Set up: Cube of DSSSD 4-6 Segmented HPGe TAS Good scheme for Neutron detection Fast Scintillators for T1/2 Neutron Detection Need to be improved!! M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  24. Outlook @ EURISOL • Shell structure @ drip lines • Changes in the (effective) interaction • New “islands” of inversion • Proton drip line and N=Z nuclei • Spectroscopy beyond the drip line • Proton-neutron pairing • Isospin Symmetry • Isospin Mixing • GT and Fermi -decays • Order to chaos • p / ratios N=Z • Production of new isotopes • New s.p. energies at large N/Z • T1/2 and Pn-values of new isotopes M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  25. Decay mechanism ? Spin ? 12C from the -decays of 12N and 12B 0+, 1+, 2+ levels selected 0.000044 1+ 15.11 0.0031 12.71 1+ 0.0046 0.0008 10.3 0,2+ 0.027 0.015 7.6542 0+ 7.285 0.013 0.019 4.4389 2+ + - 0.946 0.9722 12B 1+ 12N 1+ 0 0+ M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  26. ab All 3  events 3’s, Channel 8Be(0+) excluded Fynbo et al., PRL 91 (2003) 82502 Fynbo et al., NPA738 (2004) 59 Diget et al, NPA760 (2005) 3 Fynbo et al., Nature 433 (2005) 136 IGISOL 12C/11B 12N/12B+X p/d 12N/12B Magnet 0+,2+ 1+ M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  27. M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  28. E 64 ch: PA + TFA + CFD + A + trigger DE Charged Particle Identification: monolithic Si telescope To distinguish low energy charged particle: p, d, t, , 6He 256 detector elements á 9 mm2 32 readout channels 64 telescopes á 7 mm2 128 readout channels multiplexed to 1 ADC. TheSolid Angle is 20% of the DSSSD but needs 4 times more electronic-channels! DE stage 1 µm E stage 400 ± 15 µm M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  29. Determination ofbeta half-livesin complex backgroundconditions only pause Implanted Produced Monte Carlo Simulations • The time sequence of fragment implantation and β detection are simulated according to the experimental conditions leaving two free parameters: the lifetimes and the efficiency • The code produces time-correlation spectra in forward- and backward-time direction. • Half-life determination of several new 194-196Re, 199,200Os and 199,202Ir isotopes relevant for the r-process. • With some modifications the method can be used for continuous beams. T. Kurtukian et al, NIM, submmitted. M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  30. b+ : p→n + e+ +  d = 4.8 (4) % b- : n→p + e- +  E.C. : p + e-→n +  ft- ft+ n p n p Mirror Asymmetry & Systematics  = nuc + SCC Thomas et al., AIP Conf. Proc 681, p. 235 • Allowed Gamow-Teller transitions (log(ft)<6) • 17 couples of nuclei • 46 mirror transitions Average asymmetry d : 11 (1) % in the 1p shell (A<17) 0 (1) % in the (2s,1d) shell (17<A<40) M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  31. 11.81 MeV state  91±10% 11.28 MeV state  9 % (e,p)-scattering on 9Be assumed J = 7/2 Only the participation of the 11.81 MeV state in 9Be for the beta feeding is considered Beta feeding to the 11-12 MeV region in 9Be Fit of the high energy peak gating on the 5He(3/2-) channel M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  32. 11Be 10Be+n 9Be+2n 6He++n 2+3n 8Li+t 9Li+d 17.9 0.50 MeV 7.31 MeV 7.90 MeV 8.98 MeV 15.72 MeV 17.91 MeV 15.7 9Li+d 1974 1979 1980 1980 1983 1996  & n 8Li+t 8.9 n 2+3n 7.9 6He++n 7.3 3/2- Charged particles (and n) n 9Be  1/2- 0.5 0+  Charged particles 0 1/2+ 0 1/2+ 10Be 11Be 11Be -decay of 11Li 20.4 3/2- Q=20.4 MeV T1/2=8.5 ms 11Li  97% 3% 0.3% M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  33. 11Li, gamma rays 320 keV ½- g ½+ 11Be Q = 20.62 MeV, T 1/2= 8.2 ms b(320) = 6.3(6) % log ft = 5.73 M.J.G. Borge et al., PRC55 (97) R8 N. Aoi et al., NPA616 (97) 181c D. Morrisey et al., NPA627 (97) 222 (1s1/2)2/(0p1/2)2 ~1 M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  34. Zn Ni Fe Exotic Radioactivities 1p-radioactivity (Z,N)  p + (Z-1,N) 2p-radioactivity (Z,N)  2p + (Z-2,N) M.J.G. Borge, IEM, CSIC, Madrid (Spain)

  35. 6Li 7Li 8Li 9Li 11Li Tanihata, 1985 Halo nuclei • Energy threshold effect • Highlight by nuclear reactions • Effects in beta decay M.J.G. Borge, IEM, CSIC, Madrid (Spain)

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