Isotope half-life determination

Chlorine fluoride, 21 235, 236, 238, 240, 242, 244, 246, 247, 249 geometry of, 18 320-322 oxygenation of, 18 349 oxygen-containing, 21 245 Chlorine fluoride oxide radicals, 18 385, 386 Chlorine hydroxide, 5 219 Chlorine isotope, half-life determination, 2 ... 

Decatriene complexes with gold, 12 348 Decay method, of isotope half-life determination, 2 325... 

SPARC (Secreted Protein Acidic and Rich in Cysteine), 46 484-485 Specific activity method, of isotope half-life determination, 2 326-327 Specific interaction theory, application, 43 19-21... 

The yield of this type of recoil collection was about 10 higher yield (i.e. up to nearly 50 ) could be obtained in vacuum without the necessity of an electric field. An adaptation of this technique made possible half-life determination on isotopes with values ranging from 30 seconds to. about 20 mseconds (175) ... 

Fourteen isotopes are now recognized. 258Md has a half-life of 2 months. This isotope has been produced by the bombardment of an isotope of einsteinium with ions of helium. Eventually enough 258Md should be made to determine its physical properties. 

Determination of gold concentrations to ca 1 ppm in solution via atomic absorption spectrophotometry (62) has become an increasingly popular technique because it is available in most modem analytical laboratories and because it obviates extensive sample preparation. A more sensitive method for gold analysis is neutron activation, which permits accurate determination to levels < 1 ppb (63). The sensitivity arises from the high neutron-capture cross section (9.9 x 10 = 99 barns) of the only natural isotope, Au. The resulting isotope, Au, decays by P and y emission with a half-life of 2.7 d. 

Most areas of research and appHcations involving the use of radioisotopes require a knowledge of what radiations come from each isotope. The particular apphcation determines what type of information is needed. If the quantity of a radionuchde in a particular sample or at a particular location is to be deterrnined and this value is to be deterrnined from the y-ray spectmm, the half-life of the nucHde and the energies and intensities or emission probabiUties of the y-rays of interest must be known. Usually it is preferable to use the y-rays for an assay measurement because the d- and P-rays ate much more readily absorbed by the source material, and may not reach the sample surface having their original energies. Once these energies are altered they caimot be used to identify the parent radionuchde. 

Phosphorus has only one stable isotope, J P, and accordingly (p. 17) its atomic weight is known with extreme accuracy, 30.973 762(4). Sixteen radioactive isotopes are known, of which P is by far the most important il is made on the multikilogram scale by the neutron irradiation of S(n,p) or P(n,y) in a nuclear reactor, and is a pure -emitter of half life 14.26 days, 1.7()9MeV, rntan 0.69MeV. It finds extensive use in tracer and mechanistic studies. The stable isotope has a nuclear spin quantum number of and this is much used in nmr spectroscopy. Chemical shifts and coupling constants can both be used diagnostically to determine structural information. 

The following data are obtained for a radioactive isotope. Plot the data and determine the half-life of the isotope. 

The constant half-life of a nuclide is used to determine the ages of archaeological artifacts. In isotopic dating, we measure the activity of the radioactive isotopes that they contain. Isotopes used for dating objects include uranium-238, potassium-40, and tritium. However, the most important example is radiocarbon dating, which uses the decay of carbon-14, for which the half-life is 5730 a. 

The law of radioactive decay implies that the number of radioactive nuclei decreases exponentially with time with a characteristic half-life. Radioactive isotopes are used to determine the ages of objects. 

Equation does not contain the concentration of A, so the half-life of a first-order reaction is a constant that is independent of how much A is present. The decomposition reactions of radioactive isotopes provide excellent examples of first-order processes, as Example illustrates. We describe the use of radioactive isotopes and their half-lives to determine the age of an object in more detail in Chapter 22. 

The ratio of plutonium isotopes to 241 Am is often reported in monitoring studies as it is an important tool in dose assessment by enabling a determination of plutonium concentrations. 243Am is produced directly by the capture of two neutrons by 241 Am. The parent of241 Am is 241Pu, which constitutes about 12% of the 1% content of a typical spent fuel rod from a nuclear reactor, has a half-life of 14 years. Separation of... 

We calculated in Example 22.4 that 0.500 g would remain. That means that 4.00 g - 0.500 g = 3.50 g of the isotope will have disintegrated. (Most of the 3.50 g will produce some other isotope.) Notice the difference in the wording of Examples 22.4 and 22.5. How much remains is determined from the half-life how much decomposes is determined from the original quantity and how much remains. 

---