  A combined scattering mechanism involving the states of free electron-hole
pairs (exciton continuum) and discrete excitons as intermediate states in the
multi-phonon Raman scattering leads to (1) a strong increase of the scattering
efficiency in the presence of a high magnetic field and to (2) an outgoing
excitonic resonance: the two features are not compatible when only free pairs
(leading to a strong increase of the scattering efficiency under the applied
magnetic field) or discrete excitons (resulting in the outgoing resonance at
the excitonic gap) are taken into account.
