Biaxiality and temperature dependence of - and -layer intermediate smectic-phase structures as revealed by resonant -ray scattering

¹ School of Physics and Astronomy, University of Manchester Manchester, M13 1PL, UK
² Department of Physics, Florida State University Tallahassee, FL 32306-4350, USA
³ School of Physics and Astronomy, University of Minnesota Minneapolis, MN 55455, USA
⁴ Brookhaven National Lab, NSLS - Upton, NY 11973, USA

Received: 19 August 2005
Accepted: 19 October 2005

Abstract

High-resolution resonant X-ray diffraction experiments have been performed on free-standing films of two selenium-containing antiferroelectric liquid-crystal mixtures. Optical studies had indicated that both mixtures exhibit exceptionally wide intermediate phases, over a total range of . Through the structural information obtained from the resonant scattering data, we confirm that the intermediate phases of these mixtures show both 3-layer and 4-layer structural periodicities. Moreover, due to the stability of these phases, we report for the first time the temperature dependence of both the helicoidal pitch and distortion angle in the 3-layer phases deduced using the resonant X-ray technique. Analysis using an extension of the theory set out by Levelut and Pansu (Levelut A-M. and Pansu B., Phys. Rev. E, 60 (1999) 6803) shows that over the temperature ranges measured, the pitch changes linearly as a function of temperature whilst the distortion angle remains constant.