Visible spectroscopy of polycyclic aromatic hydrocarbons ionic derivatives: application to astrophysics

Our approach to the assignment of Polycyclic Aromatic Hydrocarbons (PAH) ca tions as carriers of some of the Diffuse Interstellar Bands (DIBs) includes two complementary studies: the recording of the electronic spectra of cold PAH cations in the gas phase; and a systematic search for possible corresp ondence in astronomical DIBs spectra. The PAH cation visible spectra were recorded via monitoring the fragmentati on ratio of the PAH(+)-argon van der Waals complex in a molecular beam as a function of the photon energy of a visible laser beam crossing the molecul ar beam. An observation campaign with the Bernard Lyot telescope at the Pic du Midi was carried out and allowed us to begin the search for corresponde nce between the bands observed in the laboratory spectra and in astronomica l spectra. (C) 2001 Elsevier Science B.V. All rights reserved.