Spectral function polar fluids

These formulas were previously used for all possible ranges of the cone angles— that is, for p [0,7t/2], but without theoretical justification. Because of the simplicity of Eq. (126a) in comparison with the formulas for the spectral function pertinent to the rigorous hat-plane model (see Section IV.C.3), the hybrid model was often applied for calculation of dielectric properties of various polar fluids. 

A general approach (VIG, GT) to a linear-response analytical theory, which is used in our work, is viewed briefly in Section V.B. In Section V.C we consider the main features of the hat-curved model and present the formulae for its dipolar autocorrelator—that is, for the spectral function (SF) L(z). (Until Section V.E we avoid details of the derivation of this spectral function L). Being combined with the formulas, given in Section V.B, this correlator enables us to calculate the wideband spectra in liquids of interest. In Section V.D our theory is applied to polar fluids and the results obtained will be summarized and discussed. 

---