Detection of Buckminsterfullerene emission in the diffuse interstellar
  medium
  Emission of fullerenes in their infrared vibrational bands has been detected
in space near hot stars. The proposed attribution of the diffuse interstellar
bands at 9577 and 9632 \AA\ to electronic transitions of the
buckminsterfullerene cation (i.e. C$_{60}^+$ ) was recently supported by new
laboratory data, confirming the presence of this species in the diffuse
interstellar medium (ISM). In this letter, we present the detection, also in
the diffuse ISM, of the 17.4 and 18.9 $\mu$m emission bands commonly attributed
to vibrational bands of neutral C$_{60}$. According to classical models that
compute the charge state of large molecules in space, C$_{60}$ is expected to
be mostly neutral in the diffuse ISM. This is in agreement with the abundances
of diffuse C$_{60}$ we derive here from observations.
