First, 14C dating method14C is the nature of the cosmic rays and atmospheric nitrogen produced by nuclear reactions. The carbon -14 not only exists in the atmosphere, with the absorption and metabolism of the organism, through the food chain into animal or human living organisms. All because of carbon in the generation side and the -14 side, at a constant rate decay, resulting in carbon -14 in nature (including all organisms) ratio and the content of carbon stable isotope -12 content remained unchanged.When the organism dies, due to the decay of carbon The new supersedes the old. stop, the decrease of -14, so the relative ratio of -14 and -12 in carbon carbon content corresponding decrease. By determination of biological fossils unearthed in the medium carbon -14 and carbon content of -12, can accurately calculate the death of the organisms (i.e. survival) in a given organism unearthed. For example the fossil, M grams of carbon (or carbon determination of the quality of -12), according to the relative ratio of various carbon isotope content of nature can be calculated, the organism is alive, the quality of carbon -14 should be m grams. But the actual measured carbon quality of -14 only m grams of 1/8, according to the half-life the biological death has been 3 for 5730 years, has been dead for seventeen thousand two hundred and ninety years. The United States radiochemist W.F. Libby has invented the method of radioactive dating, made outstanding contributions to Archaeology He was awarded the Nobel prize for chemistry in 1960Because of the very low carbon content of -14, and the half-life is very long, so -14 can accurately measure the carbon 5 to within 60 thousand years of the unearthed cultural relics, for older unearthed cultural relics, such as living in five hundred thousand years ago, Zhoukoudian Beijing man, using carbon -14 dating method is not determined to.
There are three kinds of nature of carbon isotope, stable isotopes of 12C, 13C and 14C 14C of the radioactive isotope, the half-life is 5730 years, the application of 14C mainly has two aspects: one is the determination of biological death in archaeology, radioactive dating method; the two is labeled with 14C compound as a tracer, exploration the micro motion of chemistry and life science.
