Infrared Spectroscopy of Small Astrophysically Relevant Molecules

In this work, the astrophysically relevant molecules, TiO, Al₂O and Si₂C, have been investigated in the laboratory. Molecules were produced in a laser ablation source. Intense laser pulses were focused on solid titanium, aluminum or silicon sample. Vaporized material was picked up by a reactant gas, i.e., nitrous oxide or methane, diluted in helium. The material was guided through a reaction channel, and was subsequently expanded into a vacuum chamber, where a supersonic jet was formed. This expansion adiabatically cooled down the molecules. Infrared radiation of a quantum cascade laser perpendicularly intersected the jet, which allowed the measurement of almost Doppler spectrum of Si2C around 8 µm, and parts of the Al₂O and TiO spectra around 10 µm were measured in a step-scan mode. In addition, a new fast frequency sweep technique was set up and successfully applied to extend the spectral coverage in the 10 µm region. A total of 2091 infrared transitions were identified, and were assigned to vibrational bands TiO, Al₂O and Si₂C. Additionally, selected pure-rotational transitions of Si₂C were measured around in the microwave region. Microwave radiation was created by a synthesizer and was up-converted to the 300 GHz regime by a amplifier-multiplier chain.