The setup to produce
ultracold molecules by sympathetic cooling with laser-cooled atoms. Cold molecules with
temperature around 1 K are produced by velocity filtering and guided to the microwave trap. The laser-cooled atoms with temperature around
10 uKare produced in the magneto-optical trap and guided to the microwave trap by a
moving optical molasses. The microwave frap is formed by injecting
the microwave power through the waveguide to a Fabry-Perot cavity. The trap depth
of molecules can be up to 1 K for polar molecules and 1 mK for atoms with input
power around 1 kW. Due to dipolar interaction between atoms and molecules the collision cross section is larger
eough to perform efficient sympathetic cooling.
The schematic diagram of velocity
filtering method to produce cold molecules. (a) For room temperature
molecular gas, the population fraction with velocity smaller than the most probable velocity corresponding to 1 K is
about 10-4. (b) For polar molecules in the low-field-seeking Stark states, the
quadrupole electrodes will generate a harmonic field in the central
region. This field is a two-dimensional trap for slower
molecules. (c) Slower molecules will be trapped by the quadrupole field and guided by the electrodes to high vacuum chamber.Faster moecule won't be guided by the electrodes and will be pumped away by the vacuum pump.
