Adjust the frequency of the laser until it acts like "optical
molasses" and traps the atoms in the center.
Explanation:
- The lasers will only interact with the atoms at certain frequencies,
indicated by the peak of the curve (called "resonance") in the lower
right.
- When the lasers are right at resonance, they cancel each other out
and the atoms feel no net force. I.e., they are being "squeezed" from
both directions but not slowed down.
- Doppler shifting due to the motion of the atoms, however, means that
each atom will "see" a different frequency based on what direction it
is moving.
- Making the frequency a little lower than resonance will cause atoms
moving toward the laser to "see" the resonance frequency.
- Making the frequency a little higher will cause atoms in the lasers to
speed up.
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