  The structures of interfaces of nano- and microscale objects in aqueous
solution are important for a wide variety of physical, chemical and biological
processes. Vibrational sum frequency scattering has emerged as a useful and
unique probe of the interfacial structure of nano- and microscale objects in
water. However, the full surface vibrational stretch mode spectrum has not been
measured yet, even though it would be extremely informative to do so. The
reason for this is that probing the vibrational modes of interfacial water
requires a full understanding of how the linear absorptive properties of the
bulk aqueous medium influence the sum frequency scattering process. Here, we
have simulated vibrational sum frequency scattering spectra of the interface of
nanoscale objects dispersed in water. We analyzed the effect of the infrared
pulse absorption on the outcome of surface vibrational sum frequency scattering
measurements. We find that both infrared absorption as well as the type of
optical detection can drastically modify the measured vibrational interfacial
spectrum. The observed changes comprise spectral distortion, frequency shifting
of the main vibrational stretch mode and the introducing of a new high
frequency peak. This last feature is enhanced by non-resonant interactions.
