Carbonaceous cosmic dust is mainly observed through infrared spectroscopy either in
absorption or in emission. Laboratory soot analogues of this interstellar or circumstellar
dust were produced in fuel-rich, low-pressure, premixed and flat, flames. The particles
were investigated by infrared absorption spectroscopy in the 2–15 μm
spectral region. The details of the spectral features shed some light on the structure of
the material and enable the study of its life cycle. In particular, the 8
μm band position is tentatively attributed to defects at the edge or in
the polyaromatic units of the materials, revealing these structural changes in
astrophysical dust.