Simple Atom Extreme Nucleus Laser Trapping and Probing

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 e- Å Ionization Energy of Helium Atom Level 2 3 S 1 Calculation 1 152 842 741 ± 6 MHz 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 6 He and 8 He Quantum Monte Carlo calculation 4 He 6 He Neutron 8 He Borromean Nucleus Borromean Rings Proton 4

Hadronic Probe: Scattering of 6 He & 8 He Beams 18 O 9 Be Tanihata et al, Phys Lett (1985) LBNL Elastic and inelastic collision: He on C, B 6 He 112 HC 6 He q Alkhazov et al, Nucl Phys (2002) GSI Elastic collision: He on H, 700 Me. V/u Matter distribution, matter radii 5

Atomic Energy Levels of Helium He energy level diagram 33 P 100 ns 1. 6 MHz 0, 1, 2 Cooling & Trapping at 1083 nm • Single photon kick 0. 1 m/s • Transition rate ~ 4 x 106 /s • Acceleration ~ 4 x 105 m/s 2 23 P 100 ns 0, 1, 2 389 nm Spectroscopy at 389 nm • Single photon kick 0. 3 m/s 1083 nm • Doppler shift 400 k. Hz 23 S 1 19. 82 e. V 11 S 0 A glow discharge He gas cell 6

Field (Volume) Shift E r s as M p sh ift s V ~ - 1/r d l ie ift h s F 7

Laser Cooling and Trapping Technical challenges: l Short lifetime, small samples (106 atoms/s available) l Metastable efficiency ~ 10 -5 l Precision requirement (~100 k. Hz) Magneto-Optical Trap (MOT) • Cooling: Temperature~ 1 m. K, avoid Doppler shift / width • Long observation time: 100 ms • Spatial confinement: trap size < 1 mm single atom sensitivity • Selectivity: no isotopic / isobaric interference 8

8 He @ GANIL by Antonio Villari et al. 1 Ge. V, 400 pn. A • He-8: 5 x 105 s-1 • He-6: 1 x 108 s-1 13 C Salle D 2 ECR Ion Source Mass separator 8 He+ @ 20 ke. V 8 He thermal 20 ke. V + He MOT Laser System 9

Atom Trapping of 6 He & 8 He at GANIL Atom Trap Setup ~1 x 108 6 He+/s ~5 x 105 8 He+/s He level scheme 3 3 P 2 Spectroscopy 389 nm 2 3 P 2 Trap 1083 nm Transverse cooling 389 nm Zeeman slower Xe 23 S 1 MOT 1083 nm 11 S 0 One trapped 6 He atom RF Discharge PMT Source 6 He ~ 5 x 107/s 8 He ~ 1 x 105/s Capture efficiency 1 x 10 -7 Trap 6 He ~ 5 /s 8 He ~ 1 x 10 -2/s 10

He-8 Trapped! First He-8 Atom June 15 th 2007 f 6 He 8 He t 50 k. Hz ~30 6 He atoms/s 110 k. Hz 60 atoms ~30 8 He atoms/hr 11

Isotope Shift and Field Shift : J - Dependence? 3 1 P 1 J=1 8 He 3 3 P 0, 1, 2 J=0 389 nm J=1 J=2 2 3 S 1 6 He J=1 Wang 04 Argonne 12

6 He & 8 He RMS Charge Radii 6 He 8 He -1. 464(34) -1. 026(63) 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 % Field Shift, MHz RMS RCH, fm Rp rc Rn - d. SO - MEC Mueller et al. , PRL (2007) + Ryjkov et al. , PRL (2008): He-8 mass + Sick PRC (2008): He-4 Charge Radius <RP 2> = 0. 766(12) fm 2 <RN 2> = -0. 120(5) fm 2 13

6 He & 8 He RMS Point Proton and Matter Radii Wang et al. , PRL (2004) Mueller et al. , PRL (2007) 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 15