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PM Johnson

Publications and source records attributed to PM Johnson.

4 recordsLinked to original sources
PubMed2000

Structure of the liquid-crystal ferrielectric phases as determined by ellipsometry

The unit cell structures of two ferrielectric liquid-crystal phases are determined from ellipsometric studies of freestanding films in a nondistorting rotatable electric field. A highly biaxial mode with out-of-plane distortions describes all of the data from two different compounds. Qualitative and quantitative features of the data rule out alternate models. We also present a detailed explanation for apparent inconsistencies between previous resonant x-ray and optical experiments.

Journal Article↗
PubMed2000

Ellipsometric studies of synclinic and anticlinic arrangements in liquid crystal films

The molecular arrangements in liquid crystal freestanding films are studied when smectic C* surface ordering occurs above the bulk smectic A to smectic C* transition temperature. Details of the resulting structures are resolved using ellipsometry. The behavior of the film is compound dependent. Below a critical electric field, either a synclinic or anticlinic structure may be present depending on the magnitude of the bulk spontaneous polarization. A model is presented in which the low-field anticlinic arrangement results from the interaction between polarization fluctuations at the two surfaces.

Journal Article↗