  Recent advancements in infrared frequency combs will enable recording of
coherent two-dimensional infrared spectra of gas-phase molecules with
rotational resolution (RR2DIR). We describe how RR2DIR spectra can be
controlled with polarization to enhance or suppress certain features of the
spectrum, with new polarization conditions unique to freely rotating molecules
and absent in the condensed-phase. With the polarization control methods
described here, RR2DIR spectroscopy can be a powerful tool for studying complex
gas mixtures of polyatomic molecules.
