simple atom, extreme nucleus: laser trapping and probing of he-8
DESCRIPTION
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. Å. fm. e -. Helium Atom. Ionization Energy of Helium Atom Level 2 3 S 1 Calculation1 152 842 741 ± 6 MHz - PowerPoint PPT PresentationTRANSCRIPT
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
2
Å
e-
Ionization Energy of Helium Atom
Level 2 3S1
Calculation 1 152 842 741 ± 6 MHz
Experiment 1 152 842 743 MHz
Gordon Drake, Phys. Scripta (1999)
Helium Atom
fm
3
Quantum Monte Carlo Calculations of Light Nuclei
Pieper & Wiringa. Ann. Rev. Nucl. Part. Sci. (2001)
4
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
Borromean RingsBorromean Nucleus
4He
8He
6He
QuantumMonte Carlo calculation
Proton
Neutron
5
Hadronic Probe: Scattering of 6He & 8He Beams
3.0
2.5
2.0
1.5
1.0
Inte
ract
ion
Rad
ius
(fm
)
876543
Helium Mass Number A
Tanihata et al, Phys Lett (1985)LBNL
Alkhazov et al, Nucl Phys (2002)GSI
Elastic and inelastic collision: He on C, B Elastic collision: He on H, 700 MeV/u
Matter distribution, matter radii
18O9Be
6He12C
6He1H
6He
6
Atomic Energy Levels of Helium
23S1
11S0
389 nm
1083 nm
23P0,1,2
19.82 eV
33P0,1,2
He energy level diagram
100 ns
100 ns 1.6 MHz• Single photon kick 0.1 m/s
• Transition rate ~ 4 x 106 /s
• Acceleration ~ 4 x 105 m/s2
Cooling & Trapping at 1083 nm
• Single photon kick 0.3 m/s
• Doppler shift 400 kHz
Spectroscopy at 389 nm
A glow discharge He gas cell
7
Field (Volume) Shift
AA
FS rZe
222 )0(3
2
1 10 1001E-3
0.01
0.1
1
10
100
| Iso
tope
Shi
ft |,
GH
z
Atomic number, Z
Mass shift
Field
shift
rE
s
p
V ~ - 1/r
8
Laser Cooling and Trapping
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
Technical challenges:
Short lifetime, small samples (106 atoms/s available)
Metastable efficiency ~ 10-5
Precision requirement (~100 kHz)
9
8He @ GANIL by Antonio Villari et al.
2.15 3.15
1.85
0.75
1.65
5 m
Salle D213C
• He-8: 5 x 105 s-1
• He-6: 1 x 108 s-1
8He+
@ 20 keV
8Hethermal
Laser System
MOT
ECR Ion Source
Massseparator
20 keV H
e +
1 GeV, 400 pnA
10
Atom Trapping of 6He & 8He at GANIL
~1x108 6He+/s~5x105 8He+/s
PMT
Zeemanslower
MOTTransverse
cooling389 nm
1083 nm
Atom Trap Setup
RF -Discharge
Xe
Spectroscopy389 nm
23S1
11S0
2 3P2
3 3P2
Trap1083 nm
He level scheme
Capture efficiency1x10-7
Source6He ~ 5x107/s8He ~ 1x105/s
Trap6He ~ 5 /s8He ~ 1x10-2/s
0 5 10 15 200.0
0.2
0.4
0.6
0.8
1.0
1.2
Pho
ton
coun
trat
e/ k
Hz
Time (s)
One trapped 6He atom
11
He-8 Trapped!
First He-8 AtomJune 15th 2007
t
f
-10 -8 -6 -4 -2 0 2 4 6 8 100
100
200
300
400
500
Cou
nts
per
Cha
nnel
Rel. Laser Frequency, MHz
-10 -8 -6 -4 -2 0 2 4 6 8 100
20
40
60
80
100
Cou
nts
per
Cha
nnel
Rel. Laser Frequency, MHz
50 kHz
6He
~30 6He atoms/s
110 kHz60 atoms
8He
~30 8He atoms/hr
12
0.4
0.5
0.6
0.7
0.8
0.9
-0.2
0.0
0.2
0.4
0.6
0.8
-1.6
-1.4
-1.2
-1.0
-0.8
-0.6
6,
4 -
4319
4, M
Hz
(b)
(a)
8,
4 -
6470
1, M
Hz
J = 0 J = 1 J = 2
(c)
6He8He
Fie
ld S
hift,
MH
z
J = 0 J = 1 J = 2
8He
6He
Isotope Shift and Field Shift : J - Dependence?
2 3S1
389
nm
3 3P0,1,2
J=2J=1
J=0
J=1
Wang 04Argonne
J=13 1P1
13
6He & 8He RMS Charge Radii
6He 8He
Field Shift, MHz -1.464(34) -1.026(63)
RMS RCH, fm 2.072(9) 1.961(16)
Total Uncertainty 0.4 % 0.9 %
- Statistical 0.1 % 0.6 %
- Trap Systematics 0.3 % 0.6 %
- Mass Systematics 0.1 % 0.0 %
- He-4: 1.681(4) fm 0.1 % 0.1 %
Mueller et al., PRL (2007)
+ Ryjkov et al., PRL (2008): He-8 mass
+ Sick PRC (2008): He-4 Charge Radius
Rp
rc
Rn
- SO - MEC
<RP2> = 0.766(12) fm2
<RN2> = -0.120(5) fm2
14
6He & 8He RMS Point Proton and Matter Radii
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
4He rms point-proton matter Experiment Theory
8He
6He
15
He-6 CollaborationP. 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 CollaborationP. 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, FranceG. W. F. Drake - Univ of Windsor, Canada L.-B. Wang – Los Alamos Lab