Shock-wave processing of C₆₀ in hydrogen

Abstract

Context. Interstellar carbonaceous particles and molecules are subject to intense shocks in astrophysical environments. Shocks induce a rapid raise in temperature and density which strongly affects the chemical and physical properties of both the gas and solid phases of the interstellar matter. Aims. The shock-induced thermal processing of C 60 particles in hydrogen has been investigated in the laboratory under controlled conditions up to 3900 K with the help of a material shock-tube. Methods. The solid residues generated by the exposure of a C 60 /H 2 mixture to a millisecond shock wave were collected and analyzed using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman micro-spectroscopy, and infrared micro-spectroscopy. The gaseous products were analyzed by Gas Chromatography and Cavity Ring Down Spectroscopy. Results. Volatile end-products appear above reflected shock gas temperatures of ∼2540 K and reveal the substantial presence of small molecules with one or two C atoms. These observations confirm the role played by the C 2 radical as a major product of C 60 fragmentation and less expectedly highlight the existence of a single C atom loss channel. Molecules with more than two carbon atoms are not observed in the post-shock gas. The analysis of the solid component shows that C 60 particles are rapidly converted into amorphous carbon with a number of aliphatic bridges. Conclusions. The absence of aromatic CH stretches on the IR spectra indicates that H atoms do not link directly to aromatic cycles. The fast thermal processing of C 60 in H 2 over the 800-3400 K temperature range leads to amorphous carbon. The analysis hints at a collapse of the cage with the formation of a few aliphatic connections. A low amount of hydrogen is incorporated into the carbon material. This work extends the range of applications of shock tubes to studies of astrophysical interest.

Detection of Cosmic Fullerenes in the Almahata Sitta Meteorite: Are They an Interstellar Heritage?

“…We put forward the alternative possibility that the fullerenes detected in this work could be of interstellar heritage. The remarkable thermal stability of fullerenes, both in the gas phase and in solid particles, for temperatures up to at least 2500 K (Sommer et al 1996;Biennier et al 2017) may have allowed these primitive species to survive the igneous processing conditions of the parent body as well as the impact shock events experienced by the ureilites. These fullerenes may have formed in the late phases of a massive (WR) star that ended its life near the parent molecular cloud of the SS.…”

Complex structures synthesized in shock processing of nucleobases – implications to the origins of life

“…The shock tube used in the current research is the material shock tube (MST1, (10)) in the Department of Solid State Structural Chemistry Unit, Indian Institute of Science, Bangalore, India. It is an 80 mm diameter shock tube composed of 2 m long driver section and 6 m long driven section separated by a metallic diaphragm.…”

“…To simulate the high-temperature heating effect of impactinduced shock, we have utilized Material Shock Tube 1 (MST1; Biennier et al, 2017;Singh et al, 2020) facility in the Department of Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India, and the High-Intensity Shock Tube for Astrochemistry (HISTA; Singh et al, 2020) in the Physical Research Laboratory, Ahmedabad, India. Both the shock tubes are similar in their design, and experiments were carried out and repeated at both the shock tube facilities.…”

“…So eventually, all the building blocks of life can be derived starting from the simplest of molecules. However, impact associated shock processing of amino acids, nucleobases (along with sugars) in extreme conditions largely remains unexplored (9,10). Blanke et al (11), used an impactor to process an amino acid 'soup' and observed peptide bonds to be present in the shocked solution.…”

Absorption Spectroscopy of Solid-Phase Fullerene C60 between 1.65 and 2.78 μm

“…17 Notably, the physical and chemical routes leading to the formation of fullerenes, which include bottom-up and top-down pathways, remain open to debate. [25][26][27] Photo-chemistry, 28 photo-dynamics 29 but also shock processing 30,31 studies of C 60 aim to shed light on this issue.…”