Computer Science
Scientific paper
Dec 1986
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986ipespreptq....s&link_type=abstract
M.S. Thesis Instituto de Pesquisas Espaciais, Sao Jose dos Campos (Brazil).
Computer Science
Chemical Composition, Extinction, Gold, Iridium, Meteorite Collisions, Neutron Activation Analysis, Concentration (Composition), Gamma Ray Spectrometers, Mass Spectrometers, Radiochemistry
Scientific paper
Analysis methods applied for neutron activation and radiochemistry for determination of trace elements, iridium and gold, were utilized in cosmochemistry. The concentrations analyzed were in the parts per billion band. The analysis by neutron activation determined the concentration of 1.5 gram irradiated iridium sample during 32 hours in thermal flux as 10 to the 13th power neutrons/sq cm/sec. Gamma spectrometry was performed on the samples in the course of 10 to 12 hours after 40 days of decay. In the analysis by radiochemical neutron activation, the method of chemical separation of noble metals through coprecipitation with tellurium (Stockman, 1983) was used for determination of gold and iridium. The first preliminary data of iridium in sedimentary rocks, collected in the National Territory was obtained with the application of neutron activation analysis method. These determinations of iridium are important for checking, in future work, an hypothesis of asteroidal impact as the cause of the large mass extinction observed in the transitional Cretaceous/Tertiary period (Alvarez et al, 1980) utilizing samples collected in the Southern Hemisphere.
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