Electronic spectroscopy of molecules of astrophysical interest

This thesis revolves around the electronic spectroscopy of molecules in the laboratory and the search for the carriers of the diffuse interstellar bands (DIBs). The electronic spectra of carbon chains are measured and analyzed in the lab, and the abundance of molecules in the diffuse interstellar regions of our Galaxy is quantified to provide some insight on the nature of the DIB carriers and of the environments where they might be found. In particular, cavity-enhanced absorption methods are employed to record spectra of linear hydrocarbons with which molecular constants are obtained. The wavelength positions of the electronic bands found in the lab are then compared to DIB spectra. Finally, absorption lines of interstellar OH+ are searched for in the near-UV spectra of starlight through diffuse and translucent clouds. These lines are used in deriving the abundance of OH+ and inferring the cosmic-ray ionization rates in these interstellar regions. These rates, in turn, are relevant to link to potential DIB carriers in these environments.