Delivery of Complex Organic Compounds from Evolved Stars to the Solar System

Stars in the late stages of evolution are able to synthesize complex organic compounds with aromatic and aliphatic structures over very short time scales. These compounds are ejected into the interstellar medium and distributed throughout the Galaxy. The structures of these compounds are similar to the insoluble organic matter found in meteorites. In this paper, we discuss to what extent stellar organics has enriched the primordial Solar System and possibly the early Earth

Diamond Infrared Emission Bands in Circumstellar Media

International audienceSince the discovery of small diamond grains in meteorites, the presence of such grains in the interstellar medium has been suspected. Here we report what we think to be the first unambiguous evidence of the presence of small crystallites of diamond in the dusty envelopes surrounding stars. Thanks to experimental results obtained in different laboratories on the diamond growth process, we identify two peculiar unidentified infrared emission bands at 3.43 and 3.53 μm as the vibrational modes of hydrogen-terminated crystalline facets of diamond. The intensities of these two strong features observed in the envelope of HD 97048 correspond to a mass of 10-10 to 10-9 M☉ of diamond dust at an equilibrium temperature of ~1000 K

Light-emitting silicon nanocrystals from laser pyrolysis

Crystalline Si nanoparticles with diameters between 2.5 and 20 nm are prepared by CO2-laser-induced decomposition of silane in a gas flow reactor. A small portion of the products created in the reaction zone is extracted through a nozzle into a high- acuum apparatus to form a freely propagating molecular beam of clusters and nanoparticles that can be deposited on suitable substrates. The strong visible photoluminescence (PL) of the Si nanocrystals is studied as a function of their size, and as a function of the time for which they are exposed to air. All observations can be explained on the basis of quantum confinement as the only origin of the PL. Chemical methods are exploited to modify the surface of the Si, nanoparticles and to reduce their size, thus shifting their PL to shorter wavelengths. With this technique, the Si nanoparticles, collected in much larger quantities in the filter of the flow reactor, can be made strongly luminescent so that they may be used for various applications

Interstellar dust : a new field of application for physical chemistry

The purpose of this paper is to draw the attention on the needs of astronomy in chemical physics expertise. Interstellar dust is a case in point. After summarizing briefly the state of knowledge in this field, we describe four "hot" issues, currently under closer scrutiny. Our way of addressing these issues is illustrated by the coal model of interstellar dust. We stress the need for a multidisciplinary approach, using the available techniques of materials characterization and synthesis as well as quantum theoretical chemistry