Vibrational dephasing of I₃^- in cooled ethanol solutions - where is the inhomogeneity?

The vibrational dephasing of triiodide ions is studied in ethanol solutions, at temperatures ranging from room temperature to 80 K. The dynamics of dephasing is demonstrated to be homogeneous throughout that range, and not to be dominated by population relaxation. The very mild temperature dependence of the dephasing rate, and the lack of observable inhomogeneous broadening, even in the solid, are discussed.