Experimental estimate of atomic recoil in a warm vapor

We compare the centers of the doppler-broadened absorption peaks in the 85Rb F=2 line in a (near) room temperature vacuum cell at different optical powers.

This indicate a systematic intensity-dependent shift associated with the light accelerating the atoms away from the light source. We describe the underlying physics, the experiment, the non-saturated and saturated limits of this process and a simple analytical approach we use to extract an estimate of the atomic recoil velocity.