  Atom interferometry using stimulated Raman transitions in a retroreflected
configuration is the first choice in high precision measurements because it
provides low phase noise, high quality Raman wavefront and simple experimental
setup. However, it cannot be used for atoms at zero velocity because two pairs
of Raman lasers are simultaneously resonant. Here we report a method which
allows to lift this degeneracy by using a frequency chirp on the Raman lasers.
Using this technique, we realize a Mach-Zehnder atom interferometer hybridized
with a force balanced accelerometer which provides horizontal acceleration
measurements with a short-term sensitivity of $3.2\times 10^{-5}$
m.s$^{-2}$/$\sqrt{Hz}$. We check at the level of precision of our experiment
the absence of bias induced by this method. This technique could be used for
multiaxis inertial sensors, tiltmeters or atom interferometry in a microgravity
environment.
