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Dip.Fisica - Univ.Siena  Attività di Ricerca

Recent results

We use a single modeAr⁺-pumped Ring-Dye-Laser to cool atoms  mainly with F=2->F'=3, F=2->F'=2, F=2->F'=1 transitions. A separate  single mode Ar⁺-pumped SW-Dye-Laser is needed for repumping, even when the close transition F=2->F'=3 is working.

Saturation spectroscopy allows the Cooling laser to be tuned on a specific transition. The hyperfine structures of ²P_3/2 level is resolved.

Next three plots show the expected saturation spectroscopy signal for the F=2 -> F'=1,2,3 transitions.

Next plot is obtained with fixed repump laser on D₂ line, by scanning the cooling laser. Three trapping transition are visible. Using a stronger power, the same structure keeps, but the relative intensity changes, and the F'=2 peak becomes the strongest.

This is a view of our experimental set-up; the small monitor at right is showing the cloud of trapped atoms.

A more detailed view of the cell is shown here...

... this is a B&W picture of trapped atoms inside the cell...

... and this is a short video (4sec., 98KB) of the MOT. If you cannot see the movie try first to click here, then click on the movie to start it.

Four more recent pictures of the lab and the MOT set-up.

Accurate analises have been performed of the trap behaviour as a function of the trapping frequency and of the repumping frequency detuning. This work was completed with theoretical analysis and numerical simulation, giving deep understanding of how different transitions contribute to producing both the friction force responsible for cooling down the atoms, and the spring force responsible both keeping them close to th trap center. A paper was published contatoining these results.

Further work was devoted to study a peculiar trap, which is produced in the F=1->F'=0 transition. The existence of aa trap working on such a transition is not obvious. A theoretical model accounts for that, taking into account an asymmetry induced in the decay rates to the |F=1, M=-1> and |F=1, M=+1> Zeeman sublevels by magnetically induced level mixing of the |F'=0> and |F'=1, M=0> excited states.

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