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2 new very accurate determinations of the s-wave scattering length in metastable helium

2 new very accurate determinations of the s-wave scattering length in metastable helium. Steven Moal, Maximilien Portier, Julien Dugué, Christian Buggle, Nassim Zahzam, Michèle Leduc, Claude Cohen-Tannoudji. séminaire Atomes-froids vendredi 28 octobre 2005. Study with 1 photon :

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2 new very accurate determinations of the s-wave scattering length in metastable helium

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  1. 2 new very accurate determinations of the s-wave scatteringlengthin metastable helium Steven Moal, Maximilien Portier, Julien Dugué, Christian Buggle, Nassim Zahzam, Michèle Leduc, Claude Cohen-Tannoudji séminaire Atomes-froids vendredi 28 octobre 2005

  2. Study with 1 photon : Frequency shifts of photoassociative spectra

  3. Principle of experiment 23PJ 1083 nm He* 23S1 ~19.8 eV  ~ 2 h 11S0 0u+ E S + P0 Ev = 0 (,I)  Energy 5 g+ continuum kBT S + S r v=14 R Interatomic distance

  4. Principle of experiment E E c o n t i n u u m dressed atom picture 0u+ 5 g+ S + P0 continuum Ev = 0 v=0 E=kBT kBT 0 r S + S+ ħ  v=14 Ev = 14 R

  5. Experimental result E 0u+ S + P0 v=2 v=1 v=0 R From comparison with theory Our value : a = 7.2 ± 0.5 nm

  6. Study with 2 photons : Dark atom-molecule resonances Mesure of lifetime and position of v=14

  7. 2 photon spectroscopy E 0u+ S + P0 v = 0 2 1 Energy 5 g+ S + S r v=14 R Interatomic distance

  8. From Autler-Townes to Raman effect E E E v = 0 v = 0 v = 0 1 • 2 fixed • 2 fixed 1 scanned  2 1 scanned 1 v=14 2 v=14 v=14 R R R

  9. From Autler-Townes to dark resonance 100 µW in 2nd photon 3 mW in 2nd photon 500 µW in 2nd photon 100 µW in 2nd photon 1 mW in 2nd photon 300 µW in 2nd photon

  10. From Autler-Townes to dark resonance

  11. From Autler-Townes to dark resonance 0u+ E S + P0 v=0 2 1 Energy 5 g+ continuum kBT S + S r~ -90 MHz v=14 R Interatomic distance

  12. From Autler-Townes to dark resonance 100 µW in 2nd photon 30 µW in 2nd photon 100 µW in 2nd photon 10 µW in 2nd photon 3 µW in 2nd photon

  13. Dark resonance E S–P0 v = 0 • 2 1 free atoms S–S v=14 R destructive interference between the absorption amplitude of photon 1 on the free / bound v=0 transition and of photon 2 on the bound v=0 / bound v=14 transition

  14. Mesure of Ev=14 E S + P0 v=0  2 1 kBT S + S v=14 r R shift du to T : 3kBT/2 experimentally we have 15 % less no need of the energy of v=0 Position of v=14 -91.35 ± 0.06 MHz

  15. Scattering length New value : a = 7.512 ± 0.005 nm

  16. Theoretical values Other results IOTA 2001 a=20±10 nm Stark and Meyer 1994 a=8 nm ENS 2001 a=16±8 nm ENS 2002 a<16 nm Gadéa, Dickinson and Leininger 2004 8.0<a<12.2 nm VU 2004 a=10±5 nm Przybytek and Jeziorski 2005 a=7.64±0.20 nm IOTA 2004 10.3<a<13.8 nm 2 photons Light shift x 200 7.507 7.517 0 5 10 15 20 25 30 a (nm)

  17. Mesure of lifetime v=14 v=14 has not a infinite life duration the dark resonance doesn’t go to 0 at weak intensity 0.05 < v=14 /2 < 0.3 MHz 0.5 < v=14 /2 < 3 µs Rough estimate : 4 µs from Penning collision rate between two polarized atoms Kinel = 3.10-14 cm3 s-1 (Fedichev and Shlyapnikov, 1996) 2 µW in 2nd photon 1 µW in 2nd photon 0.5 µW in 2nd photon 5 µW in 2nd photon 4 µW in 2nd photon 3 µW in 2nd photon

  18. Conclusion • 2 very accurate (and different) measurements • of the scattering length : • with frequency shift : a = 7.2 ± 0.5 nm • with dark resonance : a = 7.512 ± 0.005 nm • Creation of exotic molecules of 2 metastables • with inhibited autoionisation with • a lifeduration of 0.5 < v=14 /2 < 3 µs

  19. Soon • influence of density on v=14 • a better value for v=14 with the study of Raman signal : • in fonction of temperature • in fonction of the detuning • position and width of v=14 • in the potential S-S (M=0) • study of the 2 photons signal • during the transition • thermal cloud / BEC E S-P0 v = 0 2 , + 1 , - S-S MJ=2 v=14 2µB0 S-S MJ=0 v=14 R

  20. Other experiments Grimm, Innsbrück, April 2005 in 87Rb BEC PRL 95, 063202 (2005) • lifetime on • the dark resonance is 140 ms • 100 molecules Rb2

  21. Other experiments Lett, NIST, July 2005 in 23Na dark MOT PRA 72, 041801R 2005 • dip width around 5 MHz du to : • thermal energy distribution at T=150 µK, kBT/h~3 MHz • intensity of 2nd photon kept high

  22. No influence of the B0

  23. Principle of experiment 1.4 GHz 280 THz1083 nm 30 000 GHz =0.5 MHz

  24. Raman effect Raman pic in the red of the main line.  = -10 MHz But the main line can be shifted.  = -30 MHz Raman pic in the blue of the main line.  = few MHz

  25. Mesure of PA rate transition ? PA = 10 ms Therm = 400 ms PA = 1 ms Therm = 200 ms PA = 2 ms Therm = 100 ms PA = 5 ms Therm = 50 ms PA = 10 ms PA = 1 ms PA = 10 ms PA = 2 ms PA = 5 ms Therm = 400 ms PA = 1 ms a clear signal in the Number of atom for Therm = 0 ms we have information on PA rate transition Therm = 0 ms

  26. Black resonance 10 µW.cm-2 in 2nd photon 1 µW.cm-2 in 2nd photon

  27. séminaire du vendredi 10/06/05 Pour bientôt : MJ=0 s + MJ=2 s - E Ev=0 0 Ev=14 Ev=14

  28. E E 0u+ 5 g+ S + P0 kBT v=0 continuum r S + S + ħ  v=14 R

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