Optical Constants of Cuprous Halide Crystals in the Far-Infrared Region at 2 K

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The srin-lattice relaxation times (7't ) of trans-1,2-.dichloroethvlene (trans-DCE),cis-1,2-dichloroethylene (cis-DCE) and 1,2-dichloroethane (EDC) at atmosphericpressure were measured in a temperattn'e region of each melting point to roomtemperature. Temperature dependences of T. of cis-DCE and F,DC were those ofan ordinary and isotropic liquid, however, T.-temperature curve of trans-DCEhad a "jump" which indicates presence of a liquid-liquid phase transition at16'C. The liquid state of trams-DCE was divided into two liquid states at thistransition temperature as Lg and L. corresponding to the high and low tempera-ture states, respectively.In the L. state, a rotational motion accounts for a large part of the molecularmotion as same as other ordinary liquid. In contrast to Lj the rotational motionis suppressed and the molecules move only translationally in the L2 state.The L. state is a mesomorphic state which lacks freedom of the molecularrotational motion and is similar to a nematic phase of liquid crystals in this point.A large molecular quadrupole moment of trans-DCE plays an important role inthe ordered liquid state.
社団法人日本物理学会の論文
1981-05-15