On November 21, 2008 we, VG dell'ISSG Mazzini of Naples, we visited the Laboratory for Particle Physics CNR - INNOVA S. Nicola la Strada (Caserta). During the visit they were shown the basic elements of the methodologies used and the purpose of the analysis carried out in their respective fields of application. The problem, in fact, is to identify ions 14 C compared to other atomic species and molecular mass close. Although these contaminants are present in trace in the sample, they will in any case many orders of magnitude more abundant isotope rare. This raises the problem with high efficiency to eliminate the interference by a dispersive analysis. AMS systems this is achieved by ion beam to be in its path from the source to the detector end, a series of deflection by electric and magnetic fields that make up "filters" the combination of which results in a unique selective sensitivity . It 's so you can identify and count individually, in the final revelation, the atoms of 14 C in the sample and therefore its abundance compared stable isotope, which provides a measure of the age of the find. These characteristics make the AMS a very powerful investigative tool available to scholars of past environment in which man lived, his activities and interactions between different civilizations. In addition, the emission of large quantities of 14 C, which took place in the late '50s and early '60s because of the experiments of nuclear explosions in the atmosphere (bomb spike) provided a temporal marker that can be used to eliminate the error of dating derived precisely from this higher concentration of 14 C in the atmosphere. Also introduced were the founding principles of the method of radiocarbon dating, the particular features and advantages of the variant method with conventional accelerator compared to the radiometric method, the types of artifacts and dating age ranges, the possibility of extending the measures to other rare isotopes. Were some examples of archaeological investigations of special interest and environmental issues concerning the carbon cycle. The dating of objects of various kinds between the ages of 0 and 50,000 years can be made using the radiocarbon method, provided that it contains carbon of organic origin, as is the case for coal, wood, textiles, bones, paleo soils, etc. . The naturally occurring carbon consists of two stable isotopes (the 12 C for 98.9% and 13 C for 1, 1%), and a radioactive, the 14 C, which has an average life of 8266 years and an abundance of less than one part in 1012. The carbon contained in all living organisms in the terrestrial biosphere, due to exchange processes that characterize the life cycle of the cell (photosynthesis and metabolism of plants and animals), the same carbon isotopic composition of atmospheric carbon dioxide. The 14 C radioactive binds to atmospheric oxygen forming a molecule of 14 CO 2 ; studies on large-scale circulation of the atmosphere have shown that they are just a few years because the carbon dioxide thus produced is perfectly mixed with one containing the other isotope of carbon, so that the isotopic ratio of 14 C / 12 C of atmospheric carbon dioxide is independent of latitude, longitude and altitude considered. It 'so clear as the measure of the rate of decay (radiometric method) or relative abundance (mass spectrometry) in a current exhibit, you can get the time elapsed from the event in question. The visit in question turned out to be very interesting because it allowed us to touch certain aspects of a subject which at times can prove to be almost exclusively theoretical and abstract if studied from textbooks in addition, there is piaciuto conoscere l’utilizzo che ha lo studio delle particelle nella vita quotidiana: si pensi, ad esempio, all’esame che viene effettuato su diversi tipi di acqua e vini per verificare la quantità di 13 C presente al fine di ottenere informazioni precise sulla provenienza e sull’età , evitando quindi contraffazioni.
Napoli, 2/12/08
Classe V G, I.S.S. G. Mazzini, Napoli
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