Vibrational line shapes of liquid and subcritical carbon dioxide in nano-pores



Coherent anti-Stokes Raman spectroscopy (CARS) spectra of the Fermi-dyad ν1/2ν2 Q-branches were recorded in subcritical (T = 30.5 °C) carbon dioxide imbedded in a nano-porous glass (NG) matrix with pore size of 4 nm and in bulk. The spectral broadening of liquid carbon dioxide confined inside the pores is essentially not homogeneous in contrast to the case of the unconfined one. Analysis shows that the spectral line shape is defined by two resonant contributions provided by the core bulk molecules and those near the surface layer inside the NG pores as well as by nonresonant contributions of the glass matrix. The spectrum attributed to the molecules from near-surface layer has several times greater linewidth and is shifted to the low-wavenumber side in comparison with the spectrum in the bulk. Copyright © 2008 John Wiley & Sons, Ltd.