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Archaeometry at OSU’s Radiation Center |
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Beta decay: |
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î The compound nucleus almost instantaneously de-excites into a more stable configuration through emission of one or more prompt gamma rays ((p), with a half-life of 10-13 to 10-3 sec. In some cases, this new configuration will be stable. |
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More typically, the resulting configuration is a radioactive nucleus which further de-excites (or decays) by emission of a beta particle and one or more characteristic delayed gamma rays ((d), according to the unique half-life of the radioactive nucleus. Half-lives can range from a second to many years. It is these delayed gamma rays that are utilized by INAA for elemental determinations. Both the energy carried by the gamma ray (measured in kiloelectron volts or keV), and the rate or half-life of the decay are characteristic of a particular isotope .
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In the following equation, radioactive Al-28 decays to stable Si-28 through the loss of a beta particle. It also releases a gamma ray with a characteristic energy of 1779 keV . |