  Atom interferometry relies on the separation and recombination of atom
wavepackets. When the two paths overlap perfectly at the end of the
interferometer, the phase is insensitive to the atomic velocity distribution.
Here, we show that, when the separation and recombination is performed using a
Raman transition there is a displacement of the atomic wavepacket due to a
phase shift during light pulses. Because of the variation of the laser
intensity seen by the atoms, there is an imperfect cancellation of these
displacements. The observation of a velocity-dependent phase shift on the
interferometer is the signature of this effect, which has been modeled. Thanks
to the signature we have identified, we are able to compensate for this effect
by applying laser power ramps during the interferometer to mitigate intensity
variations.
