  The effects of particle shape on the vibrational properties of colloidal
glasses are studied experimentally. 'Ellipsoidal glasses' are created by
stretching polystyrene spheres to different aspect ratios and then suspending
the resulting ellipsoidal particles in water at high packing fraction. By
measuring displacement correlations between particles, we extract vibrational
properties of the corresponding "shadow" ellipsoidal glass with the same
geometric configuration and interactions as the 'source' suspension but without
damping. Low frequency modes in glasses composed of ellipsoidal particles with
major/minor axis aspect ratios $\sim$1.1 are observed to have predominantly
rotational character. By contrast, low frequency modes in glasses of
ellipsoidal particles with larger aspect ratios ($\sim$3.0) exhibit a mix of
rotational and translational character. All glass samples were characterized by
a distribution of particles with different aspect ratios. Interestingly, even
within the same sample it was found that small-aspect-ratio particles
participate relatively more in rotational modes, while large-aspect-ratio
particles tend to participate relatively more in translational modes.

Soft Condensed Matter;Disordered Systems and Neural Networks