The following paper gives a discussion of the methods involved in evaluating the oscillator strengths from both the dispersion and absorption equations for liquids. The resulting equations are then applied to a set of infra-red bands on which the absorption and dispersion were measured.
ARCHIE I. MAHAN†, "Oscillator Strengths for the Liquid Phase," J. Opt. Soc. Am. 31, 248-259 (1941)