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2014 La technique de spectroscopie dans le domaine du temps (SDT) est appliquée pour la première fois à l'étude des propriétés diélectriques de cristaux liquides. Nous mesurons la permittivité complexe de l'octylcyanobiphenyl (8CB) et comparons les résultats avec ceux de la littérature obtenus par les méthodes fréquentielles en régime permanent Nous montrons également qu'il est possible de définir différents domaines de relaxation à partir des résultats obtenus par la technique SDT, en effectuant des approximations successives des fonctions de distribution des temps de relaxation.Abstract. 2014 Time domain spectroscopy (TDS) is introduced for the first time to study the complex permittivity of liquid crystals. Measurements have been carried out for octylcyanobiphenyl (8CB) and the results are compared with literature data obtained by conventional steady-state methods in the frequency domain. It is also shown that the TDS results enable one to calculate successive approximations for the relaxation time distribution functions, which can be used to distinguish among different domains.

The time domain reflectometric method is used with success to measure the dielectric properties of water from 10 MHz to 8 GHz. It is shown that special precautions must be taken into account in order to determine the dielectric properties of a substance with high dielectric constant in the microwave region.

differ drastically from those of Fe(III) lattice ions in ferrisilicate.1 234 Cations are located in the local crystal field of low symmetry and are accessible to gas-phase molecules. Figure 3 shows the ESR spectrum of Fe(III) isolated cations in H-ZSM-5. The ESR line with g = 4.27 may characterize the isolated Fe(III) ion in tetrahedral or orthorhombic coordination and the formation of ESR lines with g > 4.3 is caused by the distortion of ion environment.16•17Interaction of coordinatively unsaturated Fe(III) ions with NH3, resulting in the increase of field symmetry, provokes a complete disappearance of low-field lines with g2 = 5.8 and g3 = 6.3. At the same time the temperature dependence of the intensity for the line with g = 4.3 becomes anomalous (/20 «c =* 1017 spin/g; /_196=c 2 X 1019 spin/g).4 The sorption of xenon or hexane at room temperature is accompanied by the noticeable broadening of lines with g2 = 5.8 and g3 = 6.3, as shown in Figure 3 (dotted

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