Abstract

The experimentally observed frequency dispersion of both the real index of refraction and absorption of triply distilled liquid water over the frequency domain from ω=1×10²Hz to ω=1 × 10²² Hz is described using analytic models for both the rotational and resonance polarization phenomena. In the low-frequency domain ωε[0,ω_R], where ω_R~ 1 × 10¹³ Hz, the real index of refraction monotonically decreases with increasing frequency, which is indicative of rotational polarization phenomena. The complex-valued dielectric permittivity over this frequency domain is found to be accurately described by the Rocard-Powles extension of the Debye model with two relaxation times. In the high frequency domain ω > ω_R, anomalous dispersion in the real index of refraction is observed, which is indicative of resonance polarization phenomena. The complex-valued dielectric permittivity over most of this frequency domain is found to be adequately described by a multiple resonance Lorentz-like model with a minimum of four distinct resonance frequencies. The complex-valued dielectric permittivity ε(ω) = ε_R(ω) + ε_L(ω), where ε_R(ω) is described by the multiple relaxation time Rocard-Powles model, and where ε_L(ω) is described by a multiple resonance Lorentz-like model, is fitted in a least-squares sense to the real index of refraction data. The resultant analytic description of the frequency dispersion of water is essential for the asymptotic description of ultrashort pulse propagation in that medium.

© 1991 Optical Society of America