  Raman lasers are used as a spectroscopic probe of the state of atoms confined
in a shallow 1D vertical lattice. For long enough laser pulses, resolved
transitions in the bottom band of the lattice between Wannier Stark states
corresponding to neighboring wells are observed. Couplings between such states
are measured as a function of the lattice laser intensity and compared to
theoretical predictions, from which the lattice depth can be extracted. Limits
to the linewidth of these transitions are investigated. Transitions to higher
bands can also be induced, as well as between transverse states for tilted
Raman beams. All these features allow for a precise characterization of the
trapping potential and for an efficient control of the atoms external degrees
of freedom.
