  We demonstrate an efficient eigen-decomposition method for analyzing the
guided modes in metal nanoparticle chains. The proposed method has the
advantage of showing the dispersion relation and mode quality simultaneously.
It can also separate the material and geometrical properties, so its efficiency
does not depend on the complexity of the material polarizability. The method is
applied to analyze the guided modes of a single and a pair of metal chains. The
more accurate dynamic dipole polarizability typically gives a red-shift
compared with the results obtained with the broadly used quasistatic dipole
polarizability with radiation correction.
