CARS diagnostics of phase transitions of molecular media confined in nanopores

Coherent anti-Stokes Raman Scattering (CARS) spectroscopy proved to states and phase transitions of molecular media confined in nanopores molecular layers adsorbed on the pores surface and liquid-like condensed state inside pores can be recognized using the analysis of measured CARS spectra. Phase transitions can be revealed by appearing or disappearing of corresponding contributions in measured spectra. This paper investigates the application of CARS to study condensation of carbon dioxide in different nanoporous glass samples (NGS) with pores of several nanometers. Results show that carbon dioxide turns from gas phase to condensed state inside nanopores at pressures essentially lower than expected. The observed transition from gas phase to condensed state in nanopores is connected with critical point shift to lower values of temperature and pressure in confined geometry.