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## Homework Statement

Hi

I have a question regarding the force that it used in Optical Molasses. The force is generally given by

[tex]

F = \frac{\hbar k}{2} \frac{s_0}{1 + s_0+ (2\delta/\Gamma)^2}

[/tex]

where s

_{0}is the saturation parameter. The force saturates to

[tex]

F = \frac{\hbar k}{2}

[/tex]

It is normally said that this result is a consequence of the fact that the atom can only absorb and subsequently emit a photon twice during its excited state lifetime. However this latter statement does not make sense to me intuitively. I would say that once the atom has absorbed a photon, then -- on average -- it takes a time [itex]1/\Gamma[/itex] to emit it. So the remaining factor 1/2, where does this come in when looking at the problem like this?

Best,

Niles.

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