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Single-Photon Atomic Cooling - Raizen Lab - The University of ...

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the atomic transition and is called the Doppler temperature<br />

TD ≡ Γ<br />

. (1.9)<br />

2kB<br />

This value represent a lower limit, the Doppler limit, in some laser cooling<br />

techniques. For 87 Rb the Doppler temperature is ≈ 146µK.<br />

<strong>The</strong> last important value is the recoil velocity vr. It corresponds to<br />

the velocity change an atom undergoes from absorbing or emitting a single<br />

resonant photon. It is given by<br />

vr ≡ kL<br />

, (1.10)<br />

m<br />

and has a value <strong>of</strong> ≈ 5.8mm/s in 87 Rb. <strong>The</strong> temperature associated with this<br />

velocity, the recoil temperature Tr is given by<br />

Tr ≡ 2k2 L<br />

, (1.11)<br />

mkB<br />

and has a value <strong>of</strong> ≈ 362nK in 87 Rb. This temperature is seen as the lower<br />

limit to all atomic laser cooling methods, although there are a few clever<br />

schemes which circumvent it.<br />

23

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