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Bose-Einstein condensation of metastable He

Bose-Einstein condensation of metastable He. Chris Westbrook l’Institut d’Optique, Orsay, France EPS-12 August 2002. the helium atom. …. lifetimes: 2 3 S 1  1 1 S 0 : ~ 9000 s 2 3 P 2  2 3 S 1 : ~ 100 ns 2 3 P 2  1 1 S 0 : ~ 2 s. 0. {. J =. 1. 2. 1083 nm. 2 3 P J. ….

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Bose-Einstein condensation of metastable He

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  1. Bose-Einstein condensation of metastable He Chris Westbrook l’Institut d’Optique, Orsay, France EPS-12 August 2002

  2. the helium atom … lifetimes: 23S111S0: ~ 9000 s 23P223S1: ~ 100 ns 23P211S0 : ~2 s 0 { J = 1 2 1083 nm 23PJ … 23S1 20 eV 58 nm 11S0 singlets triplets

  3. Why He*? • If laser cooling of He* is a good idea, so is evaporative cooling. • metastability: detection… • Penning ionization Strong suppression of ionization (Amsterdam) Expts: Amsterdam, Utrecht, Canberra, Paris, Orsay

  4. Apparatus

  5. MCP At the BEC transition MCP current v we measureN, T, m

  6. Summary • N0 ~ 105, n0 ~ 1013 cm-3 • scattering length a= 18 ± 8 nm • Thomas-Fermi parameter:  = N0 a/~ 103 • collision rate at TC: g = nsv~103-104 s-1 • hydrodynamic regime • quantum depletion(na3) ~ 0.01 Science, 292, 461 (2001), PRL 68, 3459 (2001)

  7. MCP Observation of ions trapped atoms He+ -30 V

  8. loss and ionization rate

  9. Trap off Analysis of ion signal • lifetime: difficult to analyse • we can measure dI/dt • and measureN, T, m n best for a "pure" BEC

  10. ion rate vs density (quasi-pure BEC)

  11. decay of the number of atoms • Independent of the ion detection • Ionization accounts for most of the loss N = f(t,b,L) O. Sirjean et al. cond-mat/0208108

  12. conclusions • Calibration of N and I is difficult. We use a to getN0. • 2 body ionization rate coeff: 310-14 cm3s-1 • 3 body ionization is important 810-2cm6s-1 • Statistical factors (2! or 3!) are important, but: 50% correction Kagan, Svistunov, Shlyapnikov, JETP Lett. 42, 209 (1985) • We need the same for a thermal cloud • and a better measurement of a.

  13. making correlated atom pairs Four wave mixing NIST: Science 398, 218 (1999) MIT: cond-mat/0203286 (2002) Atoms (photons) created in entangled pairs PRL 85, 3987 (2000) PRL 85, 3991 (2000) Data from NIST 1999

  14. detecting the pairs • Spontaneous 4 wave mixing ("perfect correlations") • Raman pulses create colliding, untrapped condensates (other ways?) • Spatial correlations become temporal correlations • |0> + |0> collisions: Inelastic rate ! MCP detector

  15. Thank you • groupe ‘hélium’: O. Sirjean, S. Seidelin, J.Gomes, R. Hoppeler D. Boiron, A.Aspect, C.W. G. Shlyapnikov • groupe d’optique atomique G. Delannoy, Y. Lecoq, F. Gerbier, R. Simon, J. Estève, C. Aussibal, M. Fauquembergue, S. Rangwala, J. Thywissen, D. Stevens, V. Savalli, P. Bouyer, N. Westbrook, I. Bouchoule

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