  In the present work, we analyze the influence of the polarization effects
taking place during the course of a 2DIR spectroscopy experiment performed on a
molecular system undergoing an intermolecular vibrational energy transfer
process. When both donor and acceptor molecules participating in the
vibrational energy transfer are embedded in a host solvent, they face
rotational diffusion that strongly distorts the resulting 2DIR spectra. It
could be expected that the difference between rotational diffusion constants
will be of particular interest. For this purpose, the polarization effects are
discussed according to the different orderings of the laser-molecule
interactions. Next, we study the distortions of the spectra as a function of
the rotational diffusion constants of the individual molecules. The knowledge
of these polarization effects are relevant to the interpretation of the
spectra. Finally, the conclusions reached in this work for a vibrational energy
transfer are valid for any other type of third-order optical process performed
on the same molecular system.
