RESUMO
We have studied the profile of the 2140 cm(-1) fundamental band of solid carbon monoxide (CO) at low temperature (10-15 K) by infrared transmission spectroscopy and by reflection absorption infrared (RAIR) spectroscopy. In particular, transmission spectra have been taken after CO had been adsorbed on a bare crystalline silicon substrate and on pre-adsorbed solid N(2) layers of different thickness. RAIR spectra have been taken after CO had been adsorbed on a bare gold substrate and on pre-adsorbed solid N(2) layers of different thickness. Laboratory spectra show that the profile of the fundamental CO band at about 2140 cm(-1) is different in the different instances considered. In particular, we have found that the relative intensity of the LO and TO modes of the CO band depends on the thickness of the N(2) layer. Here we present the experimental results and show that these can be predicted by the elementary electromagnetic theory.
Assuntos
Monóxido de Carbono/química , Nitrogênio/química , Monóxido de Carbono/efeitos da radiação , Raios Infravermelhos , Modelos Teóricos , Nitrogênio/efeitos da radiação , Óptica e Fotônica , Espectrofotometria Infravermelho , VácuoRESUMO
Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust.
Assuntos
Hidrocarbonetos/análise , Meteoroides , Silicatos/análise , Poeira Cósmica/análise , Astronave , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.
RESUMO
Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.