Dynamic registration of D₂¹⁶O absorption spectrum in silica aerogel

Abstract

Absorption spectra of the gas phase and adsorbed D₂О in the silica aerogel with nanoscale pores were investigated in 3700–5400 cm⁻¹ range using dynamic registration with Fourier Transform spectrometer IFS-125M. Two types of sample with pores of 60 nm wide – the nitrogen gas-treated and untreated aerogels – were examined. The surface treatment of the sample changes noticeably the broadband absorption of adsorbed water. Spectrum of D₂O in the pores differs from the spectrum of bulk water as for bandwidth so for band maximum. It was found that treatment of the pores by dry nitrogen leads to increasing hydrophilic properties of the material and to change water band contour. The D₂О line widths in both the aerogels exceed those of free monomer in 1.1–3 times at the same pressure. Calculations of self-broadening coefficients of the D₂O lines were performed using semi-empirical method based on the impact theory of broadening and includes the correction factors. The calculated results well agree with experimental data. Greater differences were found for the shift of the line centre. The D₂O line shifts in the treated pores significantly exceed line shifts in the untreated pores. For some lines, these shifts have the opposite sign indicating complex nature of the molecule–wall interaction.

Keywords:

• confined water
• Fourier spectrometer
• absorption spectrum
• spectral line profiles
• line width and shift coefficients

Acknowledgements

The work supported by Russian Foundation for Basic Research [grant number 13-03-98023] and program of Fundamental Investigation Russian Academy of Science [program number 3.9].