Raman spectroscopy of ion‐irradiated astrophysically relevant materials

Abstract

Solid objects in space (interstellar grains, comets, interplanetary dust particles, etc.) are continuously exposed to energetic processes, such as cosmic ion irradiation, that influence their evolution. In this paper we present an experimental study, carried out by Raman spectroscopy, of the effects induced by ion irradiation on frozen ices and refractory materials. If the irradiated ice mixture contains a relevant amount of carbon atoms, the ice is converted into an organic residue (stable at room temperature), which at high irradiation dose evolves toward a hydrogenated amorphous carbon. Here we show that material similar to that produced in the laboratory by ion irradiation of frozen ice mixtures and refractory materials can be formed in space by cosmic ion irradiation. This finding has been recently confirmed by the Stardust mission, which revealed in some of the cometary particles collected in space and returned to earth carbonaceous materials that have been processed by cosmic ion irradiation. Copyright INTRODUCTIONThe effects induced by cosmic ion irradiation on solid objects in space (interstellar grains, comets, interplanetary dust particles (IDPs), etc.) have been studied in different laboratories for several years by using different techniques of analysis, among which is Raman spectroscopy. Raman spectroscopy gives valuable information on the vibrational transitions of molecules in the solid, liquid, and gas phase. In particular, it is a powerful tool to investigate the structural properties of a given sample and therefore it has often been used to study the effects of ion-induced lattice damage in carbonaceous solids and organic compounds.1 -5 Raman spectroscopy makes it possible to perform mineralogical studies, to identify substances and chemical compounds, and to deduce structural and symmetry properties of molecules. Owing to these abilities, Raman analysis may have important applications in planetology, especially in the in situ and/or laboratory studies concerned with the evolution of surface rocks, and also in the determination of past environments, as recorded by meteorites. IDPs collected, e.g. in the earth atmosphere or in the polar ices, can also be analysed by micro-Raman spectroscopy, providing information on Ł Correspondence to: G. A. Baratta, INAF-Osservatorio Astrofisico di Catania, Via Santa Sofia 78, I95123 Catania, Italy. E-mail: gbaratta@oact.inaf.it the composition and processing suffered by their parent bodies. The 'Stardust' space mission has recently given to several laboratories in the world (including ours) the unique opportunity to study cometary particles directly collected in space from comet Wild-2. Different techniques of analysis have been used to study the Wild-2 dust grains, among which is Raman spectroscopy. In this paper we report some Raman studies carried out in our laboratory that are relevant for astrophysics. EXPERIMENTALBoth in situ macro and remote macro/micro Raman spectroscopies were used. The in situ analyses were performed in a stainless steel vacuum ...

Comparison of the Raman spectra of ion irradiated soot and collected extraterrestrial carbon

“…In Fig. 8 we illustrate a comparison between spectra of Murray and Tagish Lake carbonaceous meteorites (after Baratta et al, 2008) and the spectra of aromaticrich soots irradiated at three different fluences. Raman spectra of Murray and Tagish Lake meteorites were collected with the same setup used in this work (Catania laboratory).…”

“…Mennella et al, 2003). Irradiation processes are also important in the Solar System, as they are related to the production of complex organics in the pre-solar nebula (Muñoz-Caro et al, 2006) and on minor bodies surfaces (Brunetto et al, 2006), as well as to the alteration of pre-existing carbon (Moroz et al, 2004;Baratta et al, 2008). Moreover, many studies point out that the early Sun was much more active than today, passing through an active T-Tauri phase before entering the main sequence (e.g.…”

Organic materials in planetary and protoplanetary systems: nature or nurture?

“…Among these processes UV irradiation and cosmic ion irradiation play an important role in the life-cycle of interstellar dust (Mennella et al 2003), in the production of complex organics in the presolar nebula (Muñoz-Caro et al 2006) as well as on the surface of TNOs and other minor bodies (Brunetto et al 2006), and in the alteration of pre-existing carbon materials (Moroz et al 2004;Baratta et al 2008). Many studies point out that the early Sun was much more active than today, passing through an active T Tauri phase before reaching the main sequence (e.g., Feigelson & Montmerle 1999); such strong particle and photon radiation could have had major influences on processing material during the planetary accretion phase, and more specifically on the carbon chemistry.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part III

“…[162] The polarised Raman scattering from films of helimagnetic β-MnO 2 on MgO substrates were obtained at various temperatures in order to investigate the influence of the helimagnetic structure on the vibrational modes of β-MnO 2 . [163] Baratta et al [164] studied the Raman scattering from ion-radiated astrophysically relevant solid materials. An in situ Raman study of mineral phases formed as by-products in a rotary kiln for clinker production was published by Gastaldi et al [165] MicroRaman spectroscopy was used for the study of solid and liquid inclusions within natural samples of corrundum (Al 2 O 3 ) from various continents.…”