Intermolecular coupling in HOD solutions

Intermolecular coupling of OD oscillators from HOD in H2O has been investigated by Raman spectroscopy. The data indicate that at concentrations of HOD greater than 10 mol % the effects of intermolecular coupling of OD ⋅⋅⋅ OD pairs become noticeable. Difference spectra show a characteristic derivativelike feature with an increase of intensity around 2400 cm−1 as intermolecular coupling increases. The peak frequency of the OD stretching vibration in HOD decreases from 2525 cm−1 at infinite dilution to 2500 cm−1 in 50 mol % HOD, while the width of the OD stretching band increases from 150 cm−1 (infinite dilution) to 178 cm−1 (50 mol % HOD). Depolarization measurement indicates that the band at ∼2500 cm−1 is polarized. By comparing these difference spectra with the spectrum of OD oscillators from D2O we suggest that the major features of the D2O spectrum in the liquid state can be obtained by considering intermolecular coupling of OD oscillators.