Volume 548, December 2012
|Number of page(s)||14|
|Section||Interstellar and circumstellar matter|
|Published online||16 November 2012|
Nanostructuration of carbonaceous dust as seen through the positions of the 6.2 and 7.7 μm AIBs
Institut des Sciences Moléculaires d’Orsay, CNRS – Univ. Paris-Sud 11, UMR
2 Institut d’Astrophysique Spatiale, CNRS – Univ. Paris-Sud 11, UMR 8617, 91405 Orsay Cedex, France
3 Laboratoire de Géologie, École Normale Supérieure, UMR CNRS 8538, 75231 Paris Cedex 5, France
Received: 21 December 2011
Accepted: 8 September 2012
Context. Carbonaceous cosmic dust is observed through infrared spectroscopy either in absorption or in emission. The details of the spectral features are believed to shed some light on its structure and finally enable the study of its life cycle.
Aims. The goal is to combine several analytical tools in order to decipher the intimate nanostructure of some soot samples. Such materials provide interesting laboratory analogues of cosmic dust. In particular, spectroscopic and structural characteristics that help to describe the polyaromatic units embedded into the soot, including their size, morphology, and organisation are explored.
Methods. Laboratory analogues of the carbonaceous interstellar and circumstellar dust were produced in fuel-rich low-pressure, premixed and flat flames. The soot particles were investigated by infrared absorption spectroscopy in the 2−15 μm spectral region. Raman spectroscopic measurements and high-resolution transmission electron microscopy were performed, which offered complementary information to better delineate the intimate structure of the analogues.
Results. These laboratory analogues appeared to be mainly composed of sp2 carbon, with a low sp3 carbon content. A cross relation between the positions of the aromatic C=C bands at about 6.2 micron and the band at about 8 micron is shown to trace differences in shapes and structures of the polyaromatic units in the soot. Such effects are due to the defects of the polyaromatic structures in the form of non-hexagonal rings and/or aliphatic bridges. The role of these defects is thus observed through the 6.2 and 7.7 μm aromatic infrared band positions, and a distinction between carriers composed of curved aromatic sheets and more planar ones can be inferred. Based on these nanostructural differences, a scenario of nanograin growth and evolution is proposed.
Key words: astrochemistry / dust, extinction / ISM: general / infrared: ISM
© ESO, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.