1 / 18

séminaire interne du groupe Atomes Froids Vendredi 08 octobre 2004

Determination of the s-wave scattering length in metastable helium : experimental results with single photon photoassociation. séminaire interne du groupe Atomes Froids Vendredi 08 octobre 2004. Steven MOAL, Maximilien PORTIER, Jaewan KIM Michèle LEDUC, Claude COHEN-TANNOUDJI. 1 st STEP :

tanner
Download Presentation

séminaire interne du groupe Atomes Froids Vendredi 08 octobre 2004

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Determination of the s-wave scattering lengthin metastable helium : experimental results with single photon photoassociation séminaire interne du groupe Atomes Froids Vendredi 08 octobre 2004 Steven MOAL, Maximilien PORTIER, Jaewan KIM Michèle LEDUC, Claude COHEN-TANNOUDJI

  2. 1st STEP : TWO PHOTONS EXPERIMENT

  3. E 0u+ S + P0 v = 0 2 1 energy 5 g+ kBT S + S continuum r v=14 R interatomic distance PRINCIPLE OF EXPERIMENT

  4. 0u+ (v = 0) 0u+ (v = 0) D 1 fixed 1 scanned 2 scanned 2 fixed S + S S + S 5 g+(v=14) 5g+ (v=14) Temperature (a.u.) Temperature (a.u.) -20 -10 0 10 20 Detuning with respect v=14 (MHz) -20 -10 0 10 20 Detuning with respect v=14 (MHz) FRUSTRATED PA vs. RAMAN TRANSITION

  5. large width SOME DIFFICULTIES • a large range scan to explore • Orsay value : 11 4 nmrange of –15 MHz <  < -110 MHz • transition probabilities (FC factors) are not known precisely : • too many differents combinations of relative power. • large line width of the PA laser (3 MHz) : Temperature (a.u.) Temperature (a.u.) Temperature (a.u.) Temperature (a.u.) Detuning with respect v=14 (MHz) Detuning with respect v=14 (MHz)

  6. 2nd STEP : ONE PHOTON EXPERIMENT 1- MEASURE OF LOSS SIGNAL

  7. the loss of atoms depend of the Franck Condon factor one idea : we can measure the relative intensities of molecular lines v=4 measurement of the scattering length « a » BUT : v=3 v=2 v=1 v=0 relatives intensities of molecular lines • the loss measurement is too • noisy for a very precise value • of « a » • FC calculation is not enough • precise in our case scattering length a (a0) MESURE OF LOSS SIGNAL (1)

  8. MESURE OF LOSS SIGNAL (2) • it’s NOT very precise • a very fast non-linear effect (some 60 ISAT) • not good agreement with this reference • John L. Bohn and P. S. Julienne, Phys. Rev. A 60, 414 (1999)

  9. ONE PHOTON EXPERIMENT 2- MEASURE OF OSCILLATION OF THE CLOUD

  10. the cloud moves… THE CLOUD MOVES ! when we put one photon at resonance with different Thermalization time : … with the frequency of the trap

  11. THE CLOUD MOVES ! (2) it’s linear ! slope ratio : BUT : ? • the trap is harmonic. • for high intensities, the line is not at resonance • because of a shift with laser intensity.

  12. ONE PHOTON EXPERIMENT 3- MEASURE OF THE SHIFT WITH LASER INTENSITY

  13. DISCOVER OF A SHIFT WITH LASER INTENSITY line v=1 with 0.5 mW position = -667.7 MHz when we explore high power of PA beam : line v=1 with 4 mW position = -685.0 MHz • shift of 17.3 MHz ! • deformation of the line • at high intensities

  14. INTERPRETATION one approach :A. Simoni, P. S. Julienne et al, Phys. Rev. A 66, 63406 (2002) shift due to the continuum shift due to a bound state v = 0 Veg Veg continuum v = 14 S - S

  15. : energy of the continuum : energy of v=14 DIRECTION OF THE SHIFT • shift due to the bound state v=14 BLUE SHIFT • shift due to the continuum BLUE SHIFT contribution : if RED SHIFT RED SHIFT

  16. EXPERIMENTAL SHIFT we have a RED SHIFT for v=0 always a RED SHIFT for v=1 BUT : slope ratio : • some uncertainty on the laser intensity • difficulty in deducing absolute values of FC factor

  17. CONCLUSION for evaluation of Franck Codon factor : • the measurement of loss signal : too much uncertainty • the measurement of oscillation : ratio of 3.54  0.3 we need to understand the phenomenon of oscillations for precise value of the scattering length : • the measurement of the light shift of the molecular line BUT we need to finish the theory : to calculate accurately the shifts

  18. J=0 29.6 GHz 23PJ 1 2.29 GHz 1083 nm 2 23S1 He* 11S0 AFTER… 1- spectroscopy of D2 to continue Raman 2 photons PA with a potentiel more adapted than 0u+ 2- optical Feshbach to change the scattering length « a » with light 3- BEC in linear lattice to study Mott transition

More Related