  A theory of pump-probe spectroscopy is developed in which optical fields
drive two-quantum, Raman-like transitions between ground state sublevels. Three
fields are incident on an ensemble of atoms. Two of the fields act as the pump
field for the two-quantum transitions. The absorption or gain of an additional
probe field is monitored as a function of its detuning from one of the fields
which constitutes the pump field. Although the probe absorption spectrum
displays features common to those found in pump-probe spectroscopy of
single-quantum transitions, new interference effects are found to modify the
spectrum. Many of these features can be explained within the context of a
dressed atom picture.
