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Accueil du site > Equipes de recherche > Atomes dans monocristaux > recherche > Spectroscopie du césium

Spectroscopie du césium

On s’attend à ce que l’anisotropie du cristal se traduise par une modification des niveaux atomiques.

Context : solid helium as a matrix for foreign atoms

Solid helium is the least perturbing matrix for alkali atoms : Cs-He potential is shallower than He-He potential. Laser induced fluorescence of Cs and rare-earth atoms can be excited in the solid [A.Weis, T.Yabuzaki, M.Takami].

Isotropic bcc solid helium has been considered as a matrix to submit Cs to high electric field to measure the electron EDM [P.Moroshkin, et al., Low Temp. Phys. 32, 981 (2006)].

Anisotropic hcp solid helium has been proposed as a matrix producing a quadrupolar perturbation on Cs and enabling measurement of the PV anapole moment of its nucleus [M.A.Bouchiat, C.Bouchiat, Eur.Phys.J. D 15, 5 (2001)].

Rare-earth atoms in liquid and solid helium exhibits very narrow optical lines [K.Ishikawa, et al...P.R.B. 56, 780 (1997), Q.Hui, et al., J.L.T.P. 119, 393 (2000)] interesting for measuring by optical methods elementary excitations of the solid.

Our aims

To produce and keep a large population of Cs atoms in a controlled hcp monocrystal at T 1K in view of anapole moment measurement

To investigate rare-earth atoms as a local probe for measuring vacancy energy in hcp solid by optical methods.

Improving atom production

Production of single atoms embedded in a crystal proceed in four steps :

  • A single crystal is first nucleated and grown in the cell
  • Cesium clusters and grains are laser-sputtered on the surface of the crystal from metal above the crystal using a frequency doubled YAG laser
  • Further growth of the crystal leads to having a crystal with embedded grains and clusters
  • These clusters are sputtered into clouds of single atoms by means of amplified Ti:Sapphire laser pulses (10µJ, 850nm, 100fs)
Atomic Cs density larger than 10^{11} cm^{-3} has been obtained.

Keeping atoms for longer time

Decay time of the atomic population has been determined by recording fluorescence excited on the D1 transition (6S_{1/2} \rightarrow 6P_{1/2}).

At 1.0K, the atomic population life time may be as long as 7 days, compared to hours at 1.6 K. In time intervals when no laser is shined onto the atoms, the atomic population seems not to decay at all.

Spectroscopie du césium

L’anisotropie du cristal hcp conduit à une modification des niveaux d’énergie d’un atome qui y est implanté. Nous cherchons à exploiter ces modifications dans le cas de l’atome de césium. La structure hyperfine de l’état fondamental doit elle-même devenir anisotrope, et si cette anisotropie est suffisante, elle permettra une mesure du moment anapolaire du noyau. De même la forme de la raie d’absorption optique D2 est modifiée, et l’on (...)

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