Issue |
Europhys. Lett.
Volume 59, Number 3, August 2002
|
|
---|---|---|
Page(s) | 337 - 343 | |
Section | General | |
DOI | https://doi.org/10.1209/epl/i2002-00199-0 | |
Published online | 01 September 2002 |
Rotational diffusion in a bistable potential
1
J. Stefan Institute - Jamova 39, 1001 Ljubljana, Slovenia
2
Instituto de Física, Universidad Autónoma de San
Luis Potosí Álvaro Obregón 64, 78000 San
Luis Potosí, Mexico
3
Universität Konstanz, Fachbereich Physik - Fach M621,
D-78457 Konstanz, Germany
Received:
8
March
2002
Accepted:
8
May
2002
Using depolarized quasielastic light scattering, we have investigated the
rotational diffusion of optically anisotropic colloidal particles in a dilute
suspension subject to external electric and magnetic fields . The particles were produced by the polymerization of
nematic liquid crystal droplets, leading to birefringent colloidal spheres
whose frozen orientational order is rigidly coupled to the particle
orientation. The torque on the droplet director
originating
from the coupling of
and
to the particles'
anisotropy in the refractive index and in the diamagnetic susceptibility,
respectively, leads to a suppression of the orientational fluctuations about
the direction of the external field. We observe a strong dependence of the
measured relaxation rates on the field strength and on the orientation of the
field relative to the scattering plane. We explain our findings by a solution
of the Smoluchowski equation describing rotational diffusion in a bistable
potential
which has two equivalent minima separated by a
potential barrier whose height is proportional to
.
PACS: 05.40.Jc – Brownian motion / 82.70.Dd – Colloids / 61.30.Pq – Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems
© EDP Sciences, 2002
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