UV Raman spectroscopic study of hydrogen bonding in gibbsite and bayerite between 93 and 453 K

Raman spectra of bayerite and gibbsite (hydrargillite) were measured at 453 , 295 and 93 K and after H-D exchange at 423 K with gaseous D2O, Spectra in the O-H stretching vibration region were recorded with the use of ultravio let laser excitation, which avoided the fluorescence problem typical for th ese materials. Lowering the temperature led to a spectral resolution improv ement with additional bands resolved in the v(OH) spectrum of bayerite. It was established that the positions of the Raman bands are sensitive to the temperature of the sample. A spectral criterion based on different shifts o f band positions with temperature was proposed as a method to distinguish b etween structural OH groups forming H-bonds between hydroxide layers or in the same plane of the layer. It was found that the highest wavenumber band at 3655 cm(-1) in the spectrum of bayerite does not participate in H-bondin g. A one-to-one correspondence between Raman spectra recorded in the v(OH) and v(OD) regions upon partial H-D exchange with D2O is evidence that the m ultiplicity of spectral bands is caused by different O-H . . .O' distances in the hydroxide lattice rather than by vibrational coupling of H-bonded hy droxyls. Copyright (C) 2001 John Wiley & Sons, Ltd.