Spectral properties of gas-phase condensed fullerene-like carbon
  nanoparticles from far-ultraviolet to infrared wavelengths
  Carbon solids are ubiquitous material in the interstellar space. However, the
formation pathway of carbonaceous matter in astrophysical environments as well
as in terrestrial gas-phase condensation reactions is not yet understood. Laser
ablation of graphite in different quenching gas atmospheres such as pure He,
He/H$_2$, and He/H$_2$O at varying pressures is used to synthesize very small,
fullerene-like carbon nanoparticles. The particles are characterized by very
small diameters between 1 and 4 nm and a disturbed onion-like structure. The
soot particles extracted from the condensation zone obviously represent a very
early stage of particle condensation. The spectral properties have been
measured from the far-ultraviolet (FUV) ($\lambda$=120 nm) to the mid-infrared
(MIR) ($\lambda$=15 ~$\mu$m). The seed-like soot particles show strong
absorption bands in the 3.4 ~$\mu$m range. The profile and the intensity
pattern of the 3.4 ~$\mu$m band of the diffuse interstellar medium can be well
reproduced by the measured 3.4 ~$\mu$m profile of the condensed particles,
however, all the carbon which is left to form solids is needed to fit the
intensity of the interstellar bands. In contrast to the assumption that
onion-like soot particles could be the carrier of the interstellar ultraviolet
(UV) bump, our very small onion-like carbon nanoparticles do not show distinct
UV bands due to ($\pi-\pi$*) transitions.
