  We present a general formalism for describing stimulated Raman adiabatic
passage in a multi-level atom. The atom is assumed to have two ground state
manifolds a and b and an excited state manifold e, and the adiabatic passage is
carried out by resonantly driving the a-e and b-e transitions with
time-dependent fields. Our formalism gives a complete description of the
adiabatic passage process, and can be applied to systems with arbitrary numbers
of degenerate states in each manifold and arbitrary couplings of the a-e and
b-e transitions. We illustrate the formalism by applying it to both a simple
toy model and to adiabatic passage in the Cesium atom.
