2D Raman-THz Spectroscopy of Binary CHBr-MeOH Solvent Mixture.

Hybrid 2D Raman-terahertz (THz) spectroscopy is used to measure the interactions between two solvents paired in the binary CHBr-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 CHBr 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 CHBr-CS binary solvent mixture as well as by 1D absorption measurements of neat MeOH.