Are Fullerenes Relevant to Cosmochemistry. A New Finding

摘要

The abundances of noble gases found in primitive, carbonaceous meteorites are unexpected when compared with our Sun. Known as Q-gases (Q for some unknown carrier dubbed quintessence), this anomaly has remained a mystery since it was discovered in 1975. Q-gases are characterized by increasing depletions with decreasing atomic number (Z) relative to solar noble gases and normalized to 132Xe. This Q-gas mass fractionation is unexplained, and its investigation is important to understanding the origin of the solar system. However, the subject is fraught with controversy, in part due to the complex nature of Q and in part due to claims of some researchers that cannot be reproduced by other investigators. The topic is discussed in numerous places (e.g., 1-4), with models of Q falling into two basic categories, both involving carbon entrapment of noble gases. First (Group A), there is the conservative two-dimensional view that Q-gases are adsorbed or sorbed onto a 'labyrinth' of graphite or carbon grains (5-9), or they undergo active capture onto growing surfaces (6). Second (Group B), there is the view holding to the remarkable property of carbon discovered in 1985. Carbon can curl up into closed geometries of hexagon- and pentagon-shaped carbon-ring configurations, a property ignored completely by Group A. Group B thinks of Q as a three-dimensional structure of endohedral carbon cages like fullerenes, carbon onions, or some class of carbon nanotubes (3, 4, 10). Group B does not exclude Group A effects.