1_The cosmogenic radionuclide 14C is created in the atmosphere as the result of nuclear reactions generated by cosmic radiation. It is then oxidised in the atmosphere to take on the chemical form 14CO2, which has physical and chemical properties similar to conventional carbon dioxide. First of all, 14CO2 is formed in plant tissue through photosynthesis; then, as part of the food chain, 14C enters the bodies of herbivores and subsequently carnivores. When an animal dies, it ceases to absorb 14C from the surrounding environment and 14C activity in the corresponding sample gradually decreases due to radioactive decay. The half-life of 14C is 5730 ± 40 years, which is why this radionuclide may be used to date samples containing organic carbon. 14C may be determined by measuring its activity (using conventional methods) or using Accelerator Mass Spectrometry (AMS) to determine the 14C content in a carbon isotopic mixture (now the predominant method). The resulting activities are referenced against the radiocarbon standard and expressed as conventional radiocarbon age in BP in accordance with the Stuiver-Polach convention (1977). As 14C activity was not completely constant in the past, the resulting activities must be adjusted (calibrated) using a radiocarbon calibration curve. The INTCAL09 calibration curve is now available for terrestrial samples. For the purposes of creating these calibration curves, highly precise 14C activities are allocated ages determined using other dating methods, such as dendrochronology (Stuiver et al. 1993; Reimer et al. 2009)., 2_Software such as OxCal, CALIB and CalPal may be used for the actual calibration process, and the result is generally expressed in years AD and BC, or in calibrated BP years (once again meaning prior to 1950; however, when results are expressed in this way it can often lead to confusion with the conventional radiocarbon age). Radiocarbon dating is now one of the most precise physical dating methods in archaeology, after dendrochronology., Miriam Nývltová Fišáková., and Obsahuje seznam literatury