Vibrational relaxation of a polyatomic solute in a polyatomic supercritical fluid near the critical point

Abstract

Vibrational lifetimes and absorption spectra of the asymmetric CO stretching mode (∼1990 cm−1) of W(CO)6 in supercritical CO2 are reported as functions of solvent density and temperature. Close to the critical temperature, the observables are density independent over a twofold range of density. Possible explanations are discussed for this unique behavior.

Extrusion Foaming of Poly(Lactic acid) Blown with CO2: Toward 100% Green Material

“…In addition, the magnitude of these local inhomogeneities was found to be related to the intensity of solute-solvent interactions (23) . According to Urdahl et al (24) , this particular behavior may be seen as a liquid-like condensation, i.e. a localized phase transition of the fl uid molecules around the solute polymer because the attractive solute-solvent interaction would be greater than that between the solvent molecules.…”

Supercritical Fluids in Thermoplastics Foaming: Facts or Fallacies?

“…Under such specifi c supercritical conditions, the attractive solute-solvent interaction would be greater than that between the solvent molecules. According to Urdahl et al (25) , interactions between the solvent and the solute decrease very rapidly with the increasing distance: "a localized phase transition could occur forming a nanodroplet composed of only two or three solvent shells". Interestingly, these authors underlined that these stable structures do not change over a range of density of the solvent.…”

Atomic and Molecular Low-n Rydberg States in Near Critical Point Fluids

“…(c) The energy position of infrared absorption for the W(CO) 6 CO stretching mode in supercritical carbon dioxide at (•)33 • C[i.e.,T r ≃ 1.01] and at ( )50 • C, plotted as afunctionofρ CO 2 . Adapted from [46,47]. The solid lines in (a) -(c) are provided as a visual aid.…”

“…Therefore, the perturber induced shift is only temperature sensitive near the critical point of the perturber. Urdahl, et al [46,47] studied the W(CO) 6 T 1u asymmetric CO stretching mode doped into supercritical carbon dioxide, ethane and trifluoromethane by IR photoabsorption. All three systems show similar behavior, an example of which is presented in Fig.…”