  We report studies of state-to-state vibrational energy transfer in an
isolated polyatomic molecule driven by combined stimulated Raman adiabatic
passage (STIRAP) and counter-diabatic fields (CDF), using as vehicles selective
population of one of a pair of near degenerate states in SCCl$_2$ and enhancing
the yield of HNC in the HCN/HNC isomerization reaction. The efficiency of the
population transfer within a subset of states embedded in a dense manifold of
states is examined for the cases that the transition dipole moments between the
initial and target states are much smaller than and comparable to the
transition dipole moments between background states, and for the case that the
subset states have large transition dipole moments with the background states.
We show that, in a subset of states that is coupled to background states, a
combination of STIRAP fields and CDFs that do not individually generate
processes that are competitive with the desired population transfer can
generate greater population transfer efficiency than can ordinary STIRAP with
field strength and/or pulse duration similarly restricted. We also show that
the exact CDF for an isolated three level system is a useful approximation to
the exact CDF for three and five state systems embedded in background states,
and we report a study of the stability of the STIRAP + approximate CDF control
protocol to variation of the CDF.
