Band shift and bandwidth broadening in Raman spectra of CO2 induced by absorption into an imidazolium-based ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate, up to 15 MPa

Abstract Raman spectral changes of CO 2 induced by the absorption were evaluated for the Fermi dyad continuously up to 15 MPa of equilibrium CO 2 pressure. Little pressure dependence was observed for both the band positions and the bandwidth of the absorbed CO 2 , compared to those for neat supercritical CO 2 . Furthermore, the band positions lay at much lower values than those for neat CO 2 . The bandwidth broadening was observed for the absorbed CO 2 even in the lower pressure region. The absorption state of CO 2 is discussed from the viewpoints of structural fluctuations and interaction forces induced by the surrounding ionic liquid.