The rectangular potential well (hat) model: application to the dielectric spectra of non-associated polar liquids

A theory of the wideband dielectric response of polar molecules in a hat-li ke rectangular well potential with perfectly elastic (reflecting) conical s urface of finite depth is presented. The well represents molecular interact ion in terms of the mean-field potential. Thus, escape of dipoles across th e potential barrier so they may execute complete rotations outside the cone , is also accounted for. This model is a generalisation of the cone-confine d rotator and hybrid models, described previously by Gaiduk and Tseitlin [A dv. Chem. Phys. 87 (1994) 125; Mendeleev Commun. 1997, No. 2, p. 76]. In th is work it is shown that the model, in which both the bottom of the potenti al well and its rim are flat, so that it resembles a hat, provides an adequ ate description of the wideband spectrum (comprising the Debye relaxation a nd far infra-red regions) of orientational polarisation. The applicability of the hat model has been demonstrated for strongly absorbing liquids, such as methyl chloride, for which wideband dielectric spectra due to molecular reorientation were calculated in the [0, THz] frequency region. (C) 2000 E lsevier Science B.V. All rights reserved.