Martin Teichmann Atomes de lithium-6 ultra froids dans la ... - TEL

number of atoms / 1000
25
20
15
10
5
0
5.5. HETERONUCLEAR FESHBACH RESONANCES
53.75 53.80 53.85
B=
mT
53.90 53.95 54.00
Figure 5.19: An example for the measurement of the position of a heteronuclear
Feshbach resonance. Here we show the most interesting of
the four resonances, where the position changed with the ramping speed.
The magnetic field was ramped in 1 s from lower values, 47,5 mT for the
crosses, 53,7 mT for the dots, to the value indicated in this graph. One sees
a sharp loss of atoms.
field after the ramp. For the higher ramping speed the losses seem to
appear earlier, as the magnetic field is a bit higher at the end of the
ramp than demanded from the current supply.
The sharpness of the heteronuclear resonances asks for a very
careful calibration of the magnetic field. As a first step, we performed
an RF spectroscopy of the transition from state |6〉 to state |1〉 of 6 Li
at high field (28 mT). At this field, we performed RF sweeps, and could
determine the transition frequency with an accuracy of 0,1% by searching
for the frequency where the transfer is most efficient. Knowing the
Zeeman splitting (see for eample references [71, 129]), we can calculate
the magnetic field with the same accuracy.
We also need to include the small offset coils mentioned at the end
of section 3.4, which provide an additional magnetic field. We were able
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