Morphology-dependent resonances of nearly spherical particles in random orientation

We use precise T -matrix calculations for prolate and oblate spheroids, Chebyshev particles, and spheres cut by a plane to study the evolution of Lorenz-Mie morphology-dependent resonances (MDRs) with increasing asphericity of nearly spherical particles in random orientation. We show that, in the case of spheroids and Chebyshev particles, the deformation of a sphere by as little as one hundredth of a wavelength essentially annihilates supernarrow MDRs, whereas significantly larger asphericities are needed to suppress broader resonance features. The MDR position and profile are also affected when the deviation of the particle shape is increased from that of a perfect sphere. In the case of a sphere cut by a plane, the supernarrow MDRs are much more resistant to an increase in asphericity and do not change their position and profile. These findings are consistent with the widely accepted physical interpretation of the Lorenz-Mie MDRs.