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

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.