OH-Stretch Raman Multivariate Curve Resolution Spectroscopy of HOD/H₂O Mixtures.

Area of Science:

• Physical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Intermolecular interactions significantly influence the properties of liquid water.
• Raman spectroscopy is a powerful tool for probing molecular vibrations.
• Multivariate Curve Resolution (MCR) is a chemometric technique for spectral data analysis.

Purpose of the Study:

• To quantify the role of intermolecular OH stretching vibrational couplings in liquid water.
• To interpret experimental Raman spectra of HOD/H2O mixtures using a theoretical approach.
• To provide a molecular-level understanding of Raman-MCR experiments.

Main Methods:

• Analysis of experimental Raman spectra of HOD/H2O mixtures using the multivariate curve resolution (Raman-MCR) algorithm.
• Application of a mixed quantum-classical methodology to simulate isotropic Raman-MCR spectra.
• Separation of HOD solute-correlated spectra from bulk water spectra.

Main Results:

• The study successfully simulated isotropic Raman-MCR spectra of HOD/H2O mixtures.
• Intermolecular coupling was found to cause broadening and a red shift of the OH stretching band.
• Experimental findings were well-reproduced by the theoretical model.

Conclusions:

• The theoretical analysis provides a molecular-level interpretation of Raman-MCR experiments.
• Perturbations of the OH stretching mode in HOD are attributed to intermolecular vibrational coupling.
• These coupling effects extend beyond the immediate solvation shell of HOD molecules.