YASTREBOV, S. ... et al., 2017. Fröhlich resonance in carbon nanospiroids and the 2175 Å interstellar absorption feature. Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 393, pp.59-62.
This paper demonstrates that a free electron gas model accurately simulates the spectral dependence of optical extinction spectra for carbon spiroids under the assumption that free electrons are confined in an homogeneous spherical particle owing to the delocalisation of . π electrons that occurs in the actual spectral range. This effect can occur in the spiroid, rather than a spheroid (onion) due to the variable radii of the spiral turns as a function of distance from the centre, which are smaller than typical values for the spheroid.