Raman Spectra of Aqueous NaClO4 and NaBF4 Solutions

Abstract

The OD stretching vibration band in Raman spectra of liquid HOD containing ClO₄⁻ or BF₄⁻ ions is splitted into two components. The higher frequency band v_w is assigned to OD_w groups which are weakly H‐bonded to neighbouring anions (A): OD_w = (OD... A). In Raman spectra of fully deuterated aqueous NaClO₄ or NaBF₄ solutions the v_w band is splitted once again. The higher frequency band v_{3, wb} is attached to the partially antisymmetric stretching vibration of unsymmetrically H‐bonded D₂O molecules with a weak H‐bond at one OD group and a strong H‐bond at the other OD group (= _bDOD_w). The lower frequency band must be assigned to the symmetric stretching vibration of D₂O weakly H‐bonded to anions with both OD groups (= _wDOD_w). The bands were separated into Gaussian‐Lorentzian product functions. The OD and D₂O concentration were calculated from the band areas.