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         Grupo de Física
         Nuclear Experimental




                                Decay Studies @ EURISOL




                                      María José García Borge
                                 Instituto de Estructura de la Materia, CSIC



Florence, 13-18 January 2008                   M.J.G. Borge, IEM, CSIC, Madrid (Spain)   1
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                                Overview
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         Grupo de Física
         Nuclear Experimental


Desintegration +-EC
 Desintegration -
 Desintegration 
 Fission




                                                            Halo structure
                                                            Disappearance of magic
                                                            numbers
                                                            Exotic decays
                                                             Asymmtries
           Near the drip lines
                                                            Order to Chaos

Florence, 13-18 January 2008          M.J.G. Borge, IEM, CSIC, Madrid (Spain)    2
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                                  Decay properties of exotic nuclei
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         Grupo de Física
         Nuclear Experimental




      Global                   properties    1916     Rutherford & Wood  [Philos. Mag. 31 (1916) 379]
                                              1963     Barton & Bell identified 25Si as p
    • Short half-lives (ms)
    • High Q values
    • Low Sp/n values
          -delayed particle emission

     +   (C.E.) emission
    • Selection rules:
       • Fermi:        DT=0 ; DJ=0 ; pf = pi
       • Gamow-Teller: DT=0±1; DJ=0±1 ; pf = pi
                                                                                         E, 
    • Reduced transition probability:
                                                                                         Level density
                                 T1 / 2         K                 C
                        ft  f *                                                       Spin, Isospin
                                 B.R .      2 2    2
                                          G V   GA 
                                                        2   B(F)  B(GT)
                                                                                         -decay properties

Florence, 13-18 January 2008                   M.J.G. Borge, IEM, CSIC, Madrid (Spain)                   3
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                                Production Methods
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         Grupo de Física
         Nuclear Experimental



                                                              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
Florence, 13-18 January 2008
                                                                Point like sources
                                             M.J.G. Borge, IEM, CSIC, Madrid (Spain)               4
                                   State-of Art p spectrum ( = 4 keV) @ ISOL-Facilities
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            Grupo de Física
            Nuclear Experimental
                                                                                                         Super-conducting solenoid
                                                                                                             B=3.5 Tesla


                                   p-spectrum free     33Ar
                                   of -summing




        0                                                                  Study of the proton line shape
                           2         Ep (MeV) 3                4
                                                                            Physics beyond the SM (Björn’s Talk)
                                                       32Ar
                                                                            Isospin mixing in Fermi decays
                                                                            Configuration mixing
                                                                            Level interferences
                                                                            Spin assignment
                                                                            Excitation energies
                                                                           Adelberger & García, Hyp. Int 129 (2000) 237
    0
                           2.5                       3.5                   Bhattacharya & García in preparation
                                       Ep (MeV)
Florence, 13-18 January 2008                                  M.J.G. Borge, IEM, CSIC, Madrid (Spain)                            5
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         Grupo de Física
         Nuclear Experimental
                                Development of Targets


     Studies possible due to the development of the right target

                                                                                    VC-target
                                 32Ar




                                                                               CaO-target


                                                                             Equivalent setup
                                                                             And beam time
                                                                             ¡ Gain of a factor of
                                                                             2400 in yield!


Florence, 13-18 January 2008                   M.J.G. Borge, IEM, CSIC, Madrid (Spain)               6
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                                Fragmentation Facility /Two solutions
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         Grupo de Física
         Nuclear Experimental


            Bhattacharya & García in preparation


                                            MSU
            32Ar
                                                                     JC Thomas et al., Eur Phys J A 21 (2004) 419

                                                                                  GANIL




                                                            Counts




                                                                                                  Energy (keV)
                                                                     Strong beta summing
Florence, 13-18 January 2008                       M.J.G. Borge, IEM, CSIC, Madrid (Spain)                          7
                            First Measurement of p-p correlation in 2p-radioactivity
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         Grupo de Física
         Nuclear Experimental
                                                                                                           MSU

                                                    2002
                                                                     T1/2 and E2p
                                                                     compatible with
                                                                     Sequential &
                                                                                                     PRC76 (2007)
                                                                     direct decay                    041304R
                                                                                                     Miernik, Pfützner et al.




                                                                                                     PRL99 (2007) 192501


                                70 % of the decay



                                                                                                                 Direct
                                                                                                                 decay

PRC72 (2005) 054315

Florence, 13-18 January 2008                               M.J.G. Borge, IEM, CSIC, Madrid (Spain)                        8
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         Grupo de Física
         Nuclear Experimental
                                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, 



Florence, 13-18 January 2008                   M.J.G. Borge, IEM, CSIC, Madrid (Spain)                     9
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                                Beta delayed particle emitters
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         Grupo de Física
         Nuclear Experimental




                                                                                  Neutron Rich Nuclei

                                                                                 Halo structure
                                                                                 Disappearance
                                                                                 of magic numbers



B.Jonson & K. Riisager, NPA693 (2001) 77


Florence, 13-18 January 2008                   M.J.G. Borge, IEM, CSIC, Madrid (Spain)           10
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                       Grupo de Física
                       Nuclear Experimental
                                              The Survival of Magic Numbers
                                                                                       The shell structure and the
                                                                                            associated gaps are different
                                                                                            far from stability.
                                                                                       Existence/survival of Magic Numbers
                                                                                            depends on
                                                                                       1.    The size of the gap
                                                                                       2.    Structure of mean field near
                                                                                             Fermi level (correlations np-nh
   Number of Protons




                                                                                       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
                                                              New Magic Number              cuadrupole interaction.
                                                              No Magic
                                                              In discussion            The play of correlations can be so
                                                                                            subtle that if one adds 2p to
                                                                                            32Mg we have the double magic

                                               Number of Neutrons                           nucleus 34Si.


Florence, 13-18 January 2008                                  M.J.G. Borge, IEM, CSIC, Madrid (Spain)                    11
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                                -decay of halo nuclei
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         Grupo de Física
         Nuclear Experimental




  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

Florence, 13-18 January 2008                     M.J.G. Borge, IEM, CSIC, Madrid (Spain)   12
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                                   Beta decay of an exotic nuclei
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            Grupo de Física
            Nuclear Experimental




       20.6                        -               Even a neutron rich- nuclei
3/2-
       11
         Li8                                        emit charged particles                           1996
        3
 T1/2 = 8 ms                                                                                         17.916
                                                                                         1983        9Li+d
    1966                                                                                                      9Li
                                                                                       15.721
                                                                                       8Li+t
                                         10.59


                                                                           1980
                                          8.82
                                                             1979         8.982                         d
                                                             7.315       2+3n
                                                           9Be+2n

                                                                                0.320
                                                                                                ½-
                                                  1974
               Energías
                                                  0.504
                                                                                     
               (MeV)                     0.320
                                                 10Be+n                          11Be           ½+
                                        11Be



Florence, 13-18 January 2008                             M.J.G. Borge, IEM, CSIC, Madrid (Spain)               13
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                                     βd- spectrum of 6He
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         Grupo de Física
         Nuclear Experimental




                                     Qd(Z,A) = 3.007 – S2n(MeV);
                                                                                                                         Anthony et al.,
                                     6He, 8He, 11Li, 14Be, 17B..etc
                                                                                                                         PRC 65 (2002) 034310

                                -                                        M.J.G. Borge et al., Nucl. Phys. A560 (1993)
                                                                          664
  6He
                                     +d                                        Zhukov et al., PRC47     βd-6He
                                                                                (1993) 2937

                                                                       10-4
                                           Intensity (decay-1 MeV-1)                F.C. Baker, Phys. Lett.                           11Li
                         6Li                                                        B 322 (1994) 17


                                                                       10-5                  D. Baye et al.,
                                                                                             Prog. Th. Phys.
                                                                                             91 (1994) 271



                                                                       10-6
                                                                                                  Exploring w.f.  10 fm

                                                                          00                        500                         1000
                                                                                     Ed (keV)
Florence, 13-18 January 2008                                             M.J.G. Borge, IEM, CSIC, Madrid (Spain)                                14
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                                βd- spectrum of    11Li    @ TRIUMF
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         Grupo de Física
         Nuclear Experimental




  • Implantation in a thin, highly segmented                         Raabe et al, PRL submitted

    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 correlations
    in each pixel                                                                 βd-11Li
                                                                                                         Zhukov
                                                                                                         PRC 52
                                                                                                         (95)2461


                                                                                       Baye
                                                                                       PRC79(06)064302



Florence, 13-18 January 2008                 M.J.G. Borge, IEM, CSIC, Madrid (Spain)                     15
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                            Polarized radioactive beams: 11Li @ TRIUMF
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         Grupo de Física
         Nuclear Experimental




                            11Li            8.8
                                   3/2       8        7
                                    3/2   11Be               6.179
                                                  5              5.958

                                                             2.6 MeV



                                                             3.4 MeV


                                                          10Be




   oSpin polarized 11Li beam
   o , n, n coincidences
   oSpin and parities of 7 levels in 11Be
   assigned.                                                                   Hirayama, Phys. Lett. B 611 (2005)239

Florence, 13-18 January 2008                                M.J.G. Borge, IEM, CSIC, Madrid (Spain)                16
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                           ¿ Similar decay pattern of halo nuclei & core ?
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         Grupo de Física
         Nuclear Experimental




            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

Florence, 13-18 January 2008              M.J.G. Borge, IEM, CSIC, Madrid (Spain)                17
                                       A = 9 isobar
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         Grupo de Física
         Nuclear Experimental




                                                                                                  13.257
                                                                                     5/2-
                                       5/2-              3.4(7)
                                                       =δ≈3                                      =0.45
  3/2-



                                  (1/2,5/2)-




                                 (1/2)-
                                  3/2  -                δ=1.2±0.5

                                                                                                           54.1(15)%

                                                     δ = 0.032(3)
                                                     ≈0
                                3/2-
    Nyman et al., NPA 510 (1990) 189                                         Mikolas et al., PRC 37 (1988) 766

         PLB576 (2003)55                       F. Ajzenberg-Selove, NPA 490 (1988) 1              NP A692(2001)427

Florence, 13-18 January 2008                            M.J.G. Borge, IEM, CSIC, Madrid (Spain)                 18
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                                Charged particle emission in the 11Li-decay
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         Grupo de Física
         Nuclear Experimental




                                                            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. T. Suzuki and T. Otsuka, PRC 56(1997)847

                                                           Experiment:  doppler
                                                           broadening suggests significant
                                                           (6%) feeding of states in this
                                                           region. H.O.U. Fynbo et al., NPA736 (2004)39
Florence, 13-18 January 2008                  M.J.G. Borge, IEM, CSIC, Madrid (Spain)                19
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                                Analysis techniques
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         Grupo de Física
         Nuclear Experimental




                                                              Energy & momentum
     11Li                                                     conservation
                                  6He++n
     Beam                                                                
                                                                 p1  p2  pn  0
                                 60 g/cm2                    Momentum
                                                              reconstruction

                                                              Excitation energy of
                                                              the 1-2 system:
                                                                            
                                                              P1- 2     p1 -    p2
                                                               •Deadlayer andm 2
                                                                      m1      carbon-foil
                                                               energy losses corrected
                                                               •-background subtraction:
                                                               Efront- Eback  40 keV
Florence, 13-18 January 2008                 M.J.G. Borge, IEM, CSIC, Madrid (Spain)     20
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         Grupo de Física
         Nuclear Experimental
                                Charged Particle Coincidences
                                                                                         M. Langevin et al.,
                                                                 127º - 180º             NPA 366(1981) 449




                                                              D2            D4




Florence, 13-18 January 2008                   M.J.G. Borge, IEM, CSIC, Madrid (Spain)                    21
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                                Evidence of decay through the 7He resonance
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         Grupo de Física
         Nuclear Experimental




                                                       E11Be
                                                                    Q1
                                                                            8.33
                                                                                      Q2     7.91
                                                                      7He(gs)
                                                                         E’             6He++n
                                d  10 cm



                                                                                       Contribution of a new
            2005                 127º - 180º
                                                                                       decay channel .


                                                                                       Contribution of a state at
                                                                                       16.3 MeV ( 1 MeV) ). In
                                        2007                                           agreement with theoretical
                                                                                       expectations and previous
                                                                                       -experiment
                                 d  8.5 cm


                                    m 11 Be
            E 11 Be  E '                    E1
                                      m'
Florence, 13-18 January 2008                       M.J.G. Borge, IEM, CSIC, Madrid (Spain)                   22
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                                Universal set-up for spectroscopy studies
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         Grupo de Física


                                                                                   Set up:
         Nuclear Experimental




                                                                                   Cube of DSSSD
      7 x BC501
      Liquid scintillator
      15 cm x 30 cm
                                                                                   4-6 Segmented HPGe
                                                             Ge
                                           1.2m                                    TAS
                                   2m                                              Good scheme for Neutron
                                                                                   detection
                                                  
                                                                                   Fast Scintillators for T1/2
                  3m
                                                  Gamma    detection
                                                  • 3 Glover (4xHPGe)




                                         Neutron Detection
                                         Need to be improved!!



Florence, 13-18 January 2008                          M.J.G. Borge, IEM, CSIC, Madrid (Spain)           23
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                                Outlook @ EURISOL
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         Grupo de Física
         Nuclear Experimental



                                        Shell structure @ drip lines

                                         Changes in the (effective) interaction
 Proton drip line and N=Z nuclei         New “islands” of inversion
 •Spectroscopy beyond the
 drip line
 •Proton-neutron pairing
 •Isospin Symmetry
 •Isospin Mixing
 •GT and Fermi -decays
 • Order to chaos

 •p / ratios
                                                        Production of new isotopes
                                                         New s.p. energies at large N/Z
                                                         T1/2 and Pn-values of new isotopes



Florence, 13-18 January 2008                    M.J.G. Borge, IEM, CSIC, Madrid (Spain)        24
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                                12C   from the -decays of                   12N   and    12B
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         Grupo de Física
         Nuclear Experimental




   0+, 1+, 2+ levels selected
                                             15.11                     1+


                                                 12.71                 1+Decay
                                                                       mechanism        ?
                                             10.3                           0,2+Spin ?

                                                 7.6542
                                         7.285                              0+

                                                 4.4389                     2+
                  -                                                                             +
        12B             1+                                                                      12N
                                                 0
                                                                                                      1+
                                                                            0+
Florence, 13-18 January 2008                         M.J.G. Borge, IEM, CSIC, Madrid (Spain)               25
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                 CSIC              12C/11B                                                       IGISOL
         Grupo de Física

                      p/d
         Nuclear Experimental            12N/12B+X                              12N/12B
                                                             Magnet
                                                                                               




                                                                                            All 3  events
                                0+, 2+       1+
                                                                                          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
Florence, 13-18 January 2008                      M.J.G. Borge, IEM, CSIC, Madrid (Spain)                26
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         Grupo de Física
         Nuclear Experimental




Florence, 13-18 January 2008    M.J.G. Borge, IEM, CSIC, Madrid (Spain)   27
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                            Charged Particle Identification: monolithic Si telescope
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         Grupo de Física
         Nuclear Experimental




                                DE

                                                                                          E


                                             To distinguish low
                                              energy charged
                                                           256 detector elements á 9 mm2
                                                           t, readout
                                           particle: p, d, 32 , 6He channels
   64 telescopes á 7 mm2
   128 readout channels multiplexed
                                                              64 ch: PA + TFA + CFD +
   to 1 ADC.                                                          A + trigger
         DE stage        1 µm
                                                    The Solid Angle is 20% of the DSSSD
         E stage 400 ± 15 µm                     but needs 4 times more electronic-channels!
Florence, 13-18 January 2008                    M.J.G. Borge, IEM, CSIC, Madrid (Spain)       28
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         Grupo de Física
                                Determination of beta half-lives in complex background conditions
         Nuclear Experimental




          only pause
                                                                                       Produced     Implanted


                                                          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.
Florence, 13-18 January 2008                         M.J.G. Borge, IEM, CSIC, Madrid (Spain)           29
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                                Mirror Asymmetry & Systematics
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         Grupo de Física
         Nuclear Experimental




                                       + : p → n + e+ + 
                                                                                             ft 
 - : n → p + e- +                    E.C. : p + e- → n +                                         -1
                                                                                                  -
                                                                                             ft
                          ft-                  ft+
                                                                                    = nuc + SCC

       n                        p          n               p                    Thomas et al., AIP Conf. Proc 681, p. 235


                                                                               = 4.8 (4) %
 Allowed Gamow-Teller transitions
(log(ft)<6)
                  17 couples of nuclei
                  46 mirror transitions

          Average asymmetry  :
     11 (1) % in the 1p shell (A<17)
 0 (1) % in the (2s,1d) shell (17<A<40)

Florence, 13-18 January 2008                         M.J.G. Borge, IEM, CSIC, Madrid (Spain)                          30
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         Grupo de Física
         Nuclear Experimental
                                Beta feeding to the 11-12 MeV region in 9Be

    Fit of the high energy peak gating on
             the 5He(3/2-) channel

       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


Florence, 13-18 January 2008                     M.J.G. Borge, IEM, CSIC, Madrid (Spain)     31
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         Grupo de Física
         Nuclear Experimental
                                 -decay of   11Li

                                                 20.4          3/2-
                                                        11Li                               Q=20.4 MeV
                                                                      
                                                                                           T1/2=8.5 ms
                         11Be
                                                                                                           17.9
    &n                  10Be+n       0.50 MeV       1974                                 15.7
                                                                                                                  9Li+d
    97%                  9Be+2n       7.31 MeV       1979                                        8Li+t




                                                                                     n                    8.9
                         6He++n      7.90 MeV
  Charged                                            1980                            7.9                    2+3n
  particles
                                                                                                          7.3         3/2-
  (and n)                2+3n        8.98 MeV       1980                                6He++n
                                                                                     n
    3%                                                                                                         9Be


                         8Li+t
                                     15.72 MeV                                                   
  Charged                                            1983                    1/2-
  particles                                                                                          0+
                         9Li+d
                                     17.91 MeV       1996             0      1/2+   0.5
   0.3%                                                                                   10Be
                                                                          11Be


Florence, 13-18 January 2008                     M.J.G. Borge, IEM, CSIC, Madrid (Spain)                           32
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                                       11Li,    gamma rays
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         Grupo de Física
         Nuclear Experimental




                            320 keV
                                       ½-

                                  
                                       ½+
                                11Be




     M.J.G. Borge et al., PRC55 (97) R8                  Q = 20.62 MeV, T 1/2= 8.2 ms
     N. Aoi et al., NPA616 (97) 181c                          b(320) = 6.3(6) %
     D. Morrisey et al., NPA627 (97) 222                         log ft = 5.73


                                            (1s1/2)2/(0p1/2)2 ~1

Florence, 13-18 January 2008                       M.J.G. Borge, IEM, CSIC, Madrid (Spain)   33
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                                Exotic Radioactivities
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         Grupo de Física
         Nuclear Experimental




                                     1p-radioactivity
                                    (Z,N)  p + (Z-1,N)




    2p-radioactivity
 (Z,N)  2p + (Z-2,N)



                                                                                    Zn

                                                                          Ni

                                                                     Fe




Florence, 13-18 January 2008                       M.J.G. Borge, IEM, CSIC, Madrid (Spain)   34
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                                                                                           Tanihata,
                                   Halo nuclei
            M




          Grupo de Física                                                                  1985
          Nuclear Experimental




                                                                                 Energy threshold
                                                                                 effect
                                                                                 Highlight by nuclear
                                                                                 reactions
    6Li                      7Li      8Li    9Li
                                                                                 Effects in beta
                                                                 11Li            decay
Florence, 13-18 January 2008                     M.J.G. Borge, IEM, CSIC, Madrid (Spain)               35

				
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posted:10/2/2011
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