  Hybrid two-dimensional (2D) Raman-terahertz spectroscopy is used to measure
the interactions between two solvents pair in the binary CHBr3-MeOH mixture in
the frequency range of 1-7 THz. Changes in the cross peak signature are
monitored, originating from the coupling of an intramolecular bending mode of
CHBr3 to the collective intermolecular degrees of freedom of the mixture. The
appearance of a new cross peak in the 2D spectrum measured for solvent mixture
with MeOH molar fraction of 0.3 indicates a coupling to a new set of
low-frequency modes formed due to the hydrogen bond interactions between the
two solvents. This interpretation is supported by the measurement of the
CHBr3-CS2 binary solvent mixture as well as by 1D absorption measurements of
neat MeOH.
