The Use of Liquid Crystals in Mössbauer Studies and the Use of the Mössbauer Effect in Liquid Crystal Studies
An ordered solute ‘monocrystal’ can be obtained by dissolving iron or tin bearing molecules into the liquid crystalline material 4-n-hexoxybenzylidene-4’-n-propylaniline (HBPA) and cooling from 90°C to room temperature through the nematic and smectic A phases to the smectic H phase (T≤60°C) in a magnetic field of 9000 gauss. The smectic H structure persists to 77°K and therefore allows the observation of the quadrupole interaction as a function of the angle θ between the aligning field and the gamma direction. In particular, from the θ dependence of the area ratio (Aπ/Aσ) of the quadrupole split doublet both the sign of Vzz and the value of the molecular contribution (at 77°K) to the nuclear vibrational anisotropy (εM) have been determined for the triethyltinpalmitate molecule. Furthermore, the 6 dependence of the recoil free fraction (f) yielded the lattice contribution to the vibrational anisotropy. The above information was obtained by making use of the known ordering properties of liquid crystals in the theoretical fits to the Mössbauer data. In addition, the temperature dependence of f for a 0.2% solution of diacetylferrocene in HBPA has been observed for both the supercooled smectic H phase and the crystal phase in the range 100°–300°K. The data show that the crystal obeys the Debye model and that the smectic H structure is much less rigid and deviates significantly from the Debye prediction above 150°K.
KeywordsMossbauer Spectroscopy Nematic Phase Liquid Crystalline Phasis Lattice Contribution Debye Model
Unable to display preview. Download preview PDF.
- 1.G.H. Brown, J.W. Doane and V.D. Neff, “Structure and Physical Properties of Liquid Crystals”, D.E. Schuele and R.W. Hoffman, Eds., CRC Critical Reviews of Solid State Sciences, p. 303–379 (September 1970).Google Scholar
- 4.D.L. Uhrich, Y.Y. Hsu, D.L. Fishel and J.M. Wilson, Mol. Cryst., Liquid Cryst. (in press).Google Scholar
- 7.W. Maier and A. Saupe, Zeits. fur Naturfors. 14A, 882 (1959).Google Scholar
- 8.C. Yannoni, Second Symposium on Ordered Fluids and Liquid Crystals, American Chemical Society Meeting, New York, September 1969.Google Scholar
- 9.R.E. Detjen, D.L. Uhrich and C.F. Sheley, Phys. Letters A (in press).Google Scholar
- 12.V.I. Goldanskii and E.F. Makarov, “Fundamentals of Gamma-Resonance Spectroscopy” in Chemical Applications of Mössbauer Spectroscopy, V.I. Goldanskii and R.H. Herber, Eds., Academic Press, New York (1966).Google Scholar
- 13.J.M. Wilson and D.L. Uhrich, (to be published).Google Scholar
- 14.The x-ray measurements were made by A. de Vries, Liquid Crystal Institute, Kent State University, Kent, Ohio 44242.Google Scholar
- 15.J.G. Stevens and V.E. Stevens, Eds., “Mössbauer Effect Data Index”, Plenum Publishing Corp., New York (1970).Google Scholar
- 16.D.C. Champeney and F.W.D. Woodhams, J. Phys. B (Proc. Phys. Soc.) 1, 620 (1968).Google Scholar
- 18.S.L. Ruby and I. Pelah, “Crystals, Supercooled Liquids, and Glasses in Frozen Aqueous Solutions” in Mössbauer Effect Methodology, Vol. 6, I.J. Gruverman, Ed., Plenum Press, New York (1971).Google Scholar