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A: Fachverband Atomphysik

A 36: Ultra-Cold Atoms, Ions and BEC V (with Q)

A 36.6: Talk

Friday, March 6, 2009, 12:15–12:30, VMP 6 HS-C

Optical traps for ultracold metastable helium atoms — •Juliette Simonet — LKB ENS, Paris, France

One of the main characteristics of metastable helium atoms is their high internal energy (20 eV). This energy can be released when a metastable atom hits a surface, ejecting one electron. Therefore, using a Channeltron Electron Multiplier (CEM), one can detect atoms with a time resolution of up to 5 ns. However, this high internal energy raises the problem of inelastic Penning ionizations, following: He*+ He* -> He + He+ + e*. This process has a rate of the order of 10*10cm3.s*1 but is reduced by four orders of magnitude if the atoms are spin polarized due to total spin conservation.

We report on the progess of the set up of a dipole trap for ultracold metastable helium using a red detuned fiber laser at 1560nm. One of the aims of this optical trap is to release the constraint on the magnetic field value. We plan to measure the magnetic field dependance of inelastic collision rates initially calculated by P. O. Fedichev1, for temperatures smaller than 10µK. In a spin polarized gas of helium, the spin-spin interaction produces spin relaxation and relaxation induced Penning ionization if the polarization condition is no longer maintained.

We also present the development of a optical lattices in 1D and later in 3D. We intend to monitor the Penning ionization rate in order to follow the real-time dynamics of the Superfluid-Mott insulator quantum phase transition.