Electronic spectra of cold gas phase PAH cations: Towards the identification of the Diffuse Interstellar Bands carriers

An original experimental technique capable to produce electronic spectra of cold gas phase cations of large aromatic molecules, previously suggested a s a family of potential carriers of Diffuse Interstellar Bands (DIBs), has been developed and put to work. This achievement is demonstrated with the s pectrum of the D-2<--D-0 electronic transition of the phenanthrene cation, C14H10+, in the near infrared. The results are compared with the spectrum o f the same species isolated in a neon matrix, showing how the effect of thi s environment on the spectrum severely limits the capability of the matrix isolation technique for definite DIB assignments.