RAMAN SPIKES OF PUMP REPLETION ARE NOT SOLITONS

The experiments of Druhl, Wenzel and Carlsten [Phys. Rev. Lett. 51 (19 83) 1171] are interpreted in terms of the Inverse Spectral Transform. In particular it is proved that the anomalous spike of pump repletion in the depletion zone is not a soliton but a new manifestation of the continuous spectrum, resulting from the particular evolution of the sp ectral data induced by the boundary values of the light fields. Then i t is shown that multiple phase flips in the input Stokes seed induce a multi-spike formation, which suggests new experiments.