LARGE ORGANICS IN SPACE: LABORATORY MEASUREMENTS OF GAS PHASE SPECTRA AND DIFFUSE INTERSTELLAR BANDS

摘要

Our approach to the assignment of Polycyclic Aromatic Hydrocarbons (PAHs) cations as carriers of some of the Diffuse Interstellar Bands (DIIBs) includes two complementary studies : the recording of the electronic spectra of cold PAH cations in the gas phase, and a systematic search for possible correspondence in astronomical DIBs spectra. The PAH cation visible spectra were recorded via monitoring the fragmentation 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 molecular beam. Two observation campaigns with the TBL were carried out and allowed us to search for correspondance between the bands observSd in the laboratory spectra and in astronomical spectra, thanks to specific observational protocole and data processing. Upper-limits of abundance were determined for five PAH cations. Interstellar absorption zones identified in our spectra are of variable width and some of them are very likely the result of a combination due to several species.