Dielectric Properties of Inhomogeneous Media

Abstract

The interaction of electromagnetic (EM) radiation with molecular systems gives rise to quantized transitions between the electronic,vibrational and rotational molecular energy states which may be observed by UV/visible and infra-red ab- 12 sorption spectroscopies at frequencies above about 1 THz (10 Hz). These qu- tum spectroscopies for molecules in the gaseous,liquid and solid states form a large part of physical chemistry and chemical physics. However,if one asks a fel- –6 12 low scientist “what happens when EM radiation in the range 10 to 10 Hz is - plied to those systems”the answer is usually tentative and incomplete,which shows that a majority of scientists are unfamiliar with the dielectric dispersion and - sorption phenomena that occur in this vast frequency range due to (i) dipole - laxation arising from the reorientational motions of molecular dipoles and (ii) electrical conduction arising from the translational motions of electric charges (ions,electrons). This is the domain of Broadband Dielectric Spectroscopy (BDS). 8 At frequencies below about 10 Hz a dielectric sample is regarded as a com- * plex electrical impedance Z (?),expressed in terms of the resistance R(?) and capacitance C(?),which are frequency-dependent extensive properties (here ? =2?f/Hz where f is the measuring frequency). The intensive complex dielectric * * quantities of dielectric permittivity ? (?),electrical modulus M (?), electrical * * * conductivity ? (?) and resistivity ? (?) are immediately derivable from Z (?).