Simple Atom, Extreme Nucleus Laser Trapping and Probing of by wxr16887

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									 Simple Atom, Extreme Nucleus:
Laser Trapping and Probing of He-8



             Zheng-Tian Lu
      Argonne National Laboratory
          University of Chicago




  Funding: DOE, Office of Nuclear Physics
Helium Atom




                                         fm



              Ionization Energy of Helium Atom
         e-
              Level 2 3S1
              Calculation   1 152 842 741 ± 6 MHz
    Å
              Experiment 1 152 842 743                MHz

                                                            2
                            Gordon Drake, Phys. Scripta (1999)
Quantum Monte Carlo Calculations of Light Nuclei
                                  Pieper & Wiringa. Ann. Rev. Nucl. Part. Sci. (2001)




                                                                                   3
                         Halo Nuclei 6He and 8He
               Isotope   Half-life    Spin   Isospin   Core + Valence
                He-6     807 ms        0+      1             + 2n
                He-8     119 ms        0+      2             + 4n




  Quantum                  4He
Monte Carlo
 calculation                                 6He


                                                                     Neutron
                                     8He

                Borromean Nucleus               Borromean Rings

                                                   Proton                      4
                                      Hadronic Probe: Scattering of 6He & 8He Beams
                                                                                                  6He
                                                                   9Be                12C
                                                                                      1H
                                                    18O                  6He
                                                                                                    q
                                                                                                  6He




                          3.0
                                                                                               Alkhazov et al, Nucl Phys (2002)
                                Tanihata et al, Phys Lett (1985)                               GSI
                                LBNL
Interaction Radius (fm)




                          2.5



                          2.0



                          1.5



                          1.0
                                  3      4      5       6      7     8
                                          Helium Mass Number A
                          Elastic and inelastic collision: He on C, B          Elastic collision: He on H, 700 MeV/u
                                                                               Matter distribution, matter radii                  5
                      Atomic Energy Levels of Helium

                                             Cooling & Trapping at 1083 nm
       He energy level diagram
                                              • Single photon kick  0.1 m/s
                       100 ns  1.6 MHz
        33P   0,1,2                           • Transition rate ~ 4 x 106 /s
                                              • Acceleration   ~ 4 x 105 m/s2
                                    389 nm
                      100 ns
        23P                                  Spectroscopy at 389 nm
              0,1,2
                                              • Single photon kick  0.3 m/s
          1083 nm                             • Doppler shift  400 kHz

23S1
                         19.82 eV

11S0


                                              A glow discharge He gas cell      6
                    Field (Volume) Shift

                       2 2                                            AA
             FS       Ze   (0)   r 2
                                     2

E                       3
                           r
                                                             100
              p




                                    | Isotope Shift |, GHz
                                                              10

    s                                                          1

                                                              0.1
        V ~ - 1/r
                                                             0.01

                                                             1E-3
                                                                    1      10    100
                                                                    Atomic number, Z

                                                                                       7
                  Laser Cooling and Trapping

Technical challenges:
    Short lifetime, small samples (106 atoms/s available)
    Metastable efficiency ~ 10-5
    Precision requirement (~100 kHz)




                           Magneto-Optical Trap (MOT)
                           • Cooling: Temperature~ 1 mK,
                                              avoid Doppler shift / width
                           • Long observation time: 100 ms
                           • Spatial confinement: trap size < 1 mm
                                              single atom sensitivity
                           • Selectivity:     no isotopic / isobaric interference


                                                                                8
8He   @ GANIL by Antonio Villari et al.                              • He-8: 5 x 105 s-1
                                                                     • He-6: 1 x 108 s-1
                                   1 GeV, 400 pnA
                               13C
          Salle D2
                  ECR Ion
                  Source


      Mass                                                                    8He

      separator                                             8He+
                                                                            5m
                                                                            thermal
                                                          @ 20 keV




                                          1.65      MOT
                            2.15                 3.15
                                   0.75

                                      1.85


                                                          Laser System                     9
                Atom Trapping of 6He & 8He at GANIL

                                                                                                    He level scheme
                                                                                                                         3 3 P2
~1x108 6He+/s                Atom Trap Setup                                                     Spectroscopy
~5x105 8He+/s                                                                                       389 nm               2 3 P2
                                                                                                                   Trap
                                                                                                                 1083 nm
                                                                                                                2 3 S1
                     Transverse
                                            389 nm
                       cooling                       MOT 1083 nm                                                1 1 S0
           Xe                     Zeeman
                                   slower



                   RF -                                                                       One trapped 6He atom
                Discharge
                                                                                        1.2




                                                                Photon countrate/ kHz
                                                                                        1.0
                                              PMT                                       0.8

                                                                                        0.6
       Source          Capture efficiency         Trap
                                                                                        0.4
    6He ~ 5x107/s                              6He ~ 5 /s
                            1x10-7
    8He ~ 1x105/s                              8He ~ 1x10-2/s                           0.2

                                                                                        0.0
                                                                                           0        5       10           15       20
                                                                                                         Time (s)
                                                                                                                                  10
                                                                   He-8 Trapped!




                            First He-8 Atom
                            June 15th 2007
                             f
                                              6He                                                                             8He
                                                                                                     100
                     500
                                                               50 kHz                                80
                                                                                                                                           110 kHz
                                                           t                                                                               60 atoms
Counts per Channel




                                                                                Counts per Channel
                     400

                                                                                                     60
                     300

                                                                                                     40
                     200


                     100                                                                             20


                      0                                                                               0
                           -10 -8   -6   -4   -2   0   2       4   6   8   10                              -10 -8   -6   -4   -2   0   2   4   6   8   10
                                    Rel. Laser Frequency, MHz                                                        Rel. Laser Frequency, MHz

                                    ~30 6He atoms/s                                                                 ~30 8He atoms/hr                        11
                  Isotope Shift and Field Shift : J - Dependence?
3 1P1
            J=1
                                         0.8    (a)                                           (c)
                                                      8He
3 3P0,1,2           8,4 - 64701, MHz   0.6                                          -0.6

            J=0
                                         0.4
            J=1
                                         0.2                                          -0.8
            J=2
                                         0.0




                                                                   Field Shift, MHz
                                         -0.2                                         -1.0
389 nm




                                         0.9
                                                (b)
                                                      6He
                  6,4 - 43194, MHz




                                                                                                      6
                                         0.8                                          -1.2            He
                                                                                                      8
                                         0.7
                                                                                                      He

                                         0.6                                          -1.4
            J=1
   2 3S1                                 0.5
                                                                                                                 Wang 04
                                         0.4                                          -1.6                       Argonne
                                                J=0    J=1   J=2                             J=0    J=1    J=2
                                                                                                                    12
                       6He      & 8He RMS Charge Radii


                        6He          8He
                                                                  Rp

Field Shift, MHz      -1.464(34)   -1.026(63)                rc
RMS RCH, fm           2.072(9)     1.961(16)
Total Uncertainty       0.4 %        0.9 %
- Statistical           0.1 %        0.6 %        Rn
- Trap Systematics      0.3 %        0.6 %
- Mass Systematics      0.1 %        0.0 %
- He-4: 1.681(4) fm     0.1 %        0.1 %


                                                 - SO - MEC
    Mueller et al., PRL (2007)
    + Ryjkov et al., PRL (2008): He-8 mass             <RP2> = 0.766(12) fm2
    + Sick PRC (2008): He-4 Charge Radius              <RN2> = -0.120(5) fm2
                                                                               13
6He   & 8He RMS Point Proton and Matter Radii

                              4              rms point-proton         matter
                               He                                               Experiment
                                                                                Theory

                                    6
                                        He




                                    8
                                    He




 Wang et al., PRL (2004)
Mueller et al., PRL (2007)   1.4    1.6       1.8     2.0       2.2       2.4   2.6    2.8
                                                     Nuclear Radii, fm


                                                                                             14
                                            He-6 Collaboration
    P. Mueller, L.-B. Wang, K. Bailey, J.P. Greene, D. Henderson, R.J. Holt, R. Janssens, C.L. Jiang,
        Z.-T. Lu, T.P. O’Conner, R.C. Pardo, K.E. Rehm, J.P. Schiffer,X.D. Tang - Physics, Argonne
                                  G. W. F. Drake - Univ of Windsor, Canada

                                            He-8 Collaboration
P. Mueller, K. Bailey, R. J. Holt, R. V. F. Janssens, Z.-T. Lu, T. P. O'Connor, I. Sulai - Physics, Argonne; M.-
                   G. Saint Laurent, J.-Ch. Thomas, A.C.C. Villari - GANIL, Caen, France
                 G. W. F. Drake - Univ of Windsor, Canada L.-B. Wang – Los Alamos Lab




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