  The aim of this study was to determine the strengths of the coupling of
electrons with the polar long-wavelength transverse optical (TO) vibrations
from infrared spectroscopy data. This determination is made by means of a
simple relationship between the electron-TO-phonon interaction constant and
material parameters, based on a parametrization of the electron-TO-phonon
coupling in terms of the long-range dipole-dipole interaction. The combination
of experimental data employed here allowed us to calculate directly the
relevant constants for a number of representative polar insulators and to show
that in ferroelectrics the interband electron-TO-phonon interaction at the
Gamma point is essentially strong. In these calculations, infrared spectroscopy
methods proved to be an effective tool for study of the main properties of
electron interaction with polar long-wavelength TO phonons.
