  High Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffraction
(XRD) and Raman spectroscopy reveal a polyhedral multi-shell fullerene-like
structure of astralen carbon nanoparticles. The polyhedra consist of large flat
graphitic faces connected by defective edge regions with presumably
pentagon-like structure. The faces comprise a stacking of 20-50 planar graphene
sheets with inter-sheet distance of ~ 0.340 nm. Average sizes of the particles
and their flat faces are ~ 40 nm and ~ 15 nm, respectively. The astralen
particles are suggested to have defect-free sp^2 flat faces and all defects
condense at their polyhedral edges. Electron Paramagnetic Resonance (EPR)
spectra of polycrystalline astralen samples reveal two components: a very broad
signal with DHpp > 1 T and an asymmetric narrow one centered close to g = 2.00.
The latter consists of two overlapping Lorentzian lines. All spectral
components are independent of ambient pressure. The intensities of all EPR
signals show no changes on decreasing temperature from T = 300 K down to 4 K
demonstrating the Pauli paramagnetism. Electron spin-lattice relaxation times
T1e remain very short within the same temperature range. Temperature dependent
13C Nuclear Magneti? Resonance (NMR) measurements yield nuclear spin-lattice
relaxation times T1n ~ T^-0.612. The exponent in the T1n(T)-dependence for
astralen falls between the metallic behavior, T1n ~ T^-1 (Korringa relation),
and the semiconductor behavior, T1n ~T^-0.5. All unusual magnetic resonance
features of astralen are attributed to delocalized charge carriers which amount
considerably exceeds that of spins localized in defects on multi-shell
polyhedra edges.
