  The inclusion of atomic inversion in Raman scattering can significantly alter
field dynamics in plasmonic settings. Our calculations show that large local
fields and femtosecond pulses combine to yield: (i) population inversion within
hot spots; (ii) gain saturation; and (iii) conversion efficiencies
characterized by a switch-like transition to the stimulated regime that spans
twelve orders of magnitude. While in Raman scattering atomic inversion is
usually neglected, we demonstrate that in some circumstances full accounting of
the dynamics of the Bloch vector is required.
