  The electro-rotation (EROT) and electro-orientation (EOR) behavior of
metallodielectric (MD) spherical Janus particles (JP) are studied analytically
and verified experimentally. This stands in contrast to previous either
heuristic or numerically computed models of JP dipoles. First, we obtain
frequency-dependent analytic expressions for the corresponding dipole terms for
a JP composed of a dielectric and metallic hemispheres, by applying the
standard (weak-field) electrokinetic model and using a Fourier-Legendre
collocation method for solving two sets of linear equations. EROT and EOR
spectra, describing the variation of the JP angular velocity on the forcing
frequency of a rotating and non-rotating spatially uniform electric field,
respectively, are explicitly determined and compared against experiments
(different JP size and solution conductivity). A favorably good qualitative
agreement between theory and experimental measurements was found.
