Gamma emissions, 812 table

Table 2. Half-lives and main emissions of the "Radon daughters". The alpha emissions are considered to be the source of biological damage to the respiratory system, the beta and gamma emissions depositing, relatively, a very small amount of energy in the target tissues.

The list of links to the evaluated data is at http //www. nucleide.org/DDEP WG/DDEPdata. htm. The linked. pdf format files, one for each nuclide, are very comprehensive. At the time of writing, 129 nuclides are covered. Links are also given to the ENSDF data for the same nuclides. When using the. pdf files, for normal gamma spectrometry purposes, users should take care to take emission data from the Emission tables, not from the Gamma Transitions tables. 

Radioactivity is the spontaneous emission of radiation from an unstable nucleus. Alpha (a) radiation consists of helium nuclei, small particles containing two protons and two neutrons (fHe). Beta (p) radiation consists of electrons ( e), and gamma (y) radiation consists of high-energy photons that have no mass. Positron emission is the conversion of a proton in the nucleus into a neutron plus an ejected positron, e or /3+, a particle that has the same mass as an electron but an opposite charge. Electron capture is the capture of an inner-shell electron by a proton in the nucleus. The process is accompanied by the emission of y rays and results in the conversion of a proton in the nucleus into a neutron. Every element in the periodic table has at least one radioactive isotope, or radioisotope. Radioactive decay is characterized kinetically by a first-order decay constant and by a half-life, h/2, the time required for the... 

Analytical applications have been found for all parts of the electromagnetic spectrum ranging from microwaves through visible radiation to gamma (y) rays (Table 1). The emission and absorption of electromagnetic radiation are specific to atomic and molecular processes and provide the basis for sensitive and rapid methods of analysis. There are two general analytical approaches. In one, the sample is the source of the radiation in the other, there is an external source and the absorption or scattering of radiation by the sample is measured. Emission from the sample may be spontaneous, as in radioactive decay, or stimulated by thermal or other means, as in flame photometry and fluorimetry. Both approaches can be used to provide qualitative and quantitative information about the atoms present in, or the molecular structure of, the sample. 

Because gamma rays are massless, the emission of gamma rays by themselves cannot result in the formation of a new atom. Table 4-3 summarizes the basic characteristics of alpha, beta, and gamma radiation. 

Examples of reactions proceeding during stellar nucleosynthesis are shown in Table 1. To illustrate the sequence of events, the decay series of uranium-238 is depicted in this table. Radiogenic nuclides decay by the emission of alpha, beta and gamma radiation or by electron capture into so called daughter nuclides at their half-lives. This half-life ranges from parts of seconds to billions of years. 

This table is mainly based on a similar table in BNL 325 with some additions. (See the comments preceding the references to the experimental work.) The basic theory is given in the text of this article. Fy, etc. are the partial level width for decay by neutron, gamma ray, etc. emission. The factor gF appears in the theory, where g is a spin weight factor J if two compound spin states are possible. In most cases g is not known, but is taken to be j. The quoted uncertainties in F and F = F include estimated uncertainties in Fy, but not in g, in the analysis for F. ... 

Radioactive decay processes involve the emission of a particle and/or photon (a gamma ray) from the nucleus of an atom. (See Chemical Connection 5.3.8.1 Radioactive Decay—A First-Order Reaction). Alpha decay is the ejection of an alpha particle from the nucleus of the atom (Equation 5.3.8.1) and produces a daughter nucleus that has two fewer protons and a decrease of four mass units. The velocity of the alpha particle accounts for the energy range of 4-6 MeV shown in Table 5.3.8.1. While alpha radiation can cause damage to tissues, it can only do so if the source is ingested or inhaled because the energy of alpha emitters is usually very weak and can readily be stopped by a sheet of paper. 

Positron annihilation lifetime spectroscopy (PALS) is normally applied to determine the free volume properties of a cured thermoset. The theory and methodology of PALS [27, 28] is briefly described next. The positron, an antiparticle of an electron, is used to investigate the free volume between polymer chains. The birth of the positron can be detected by the release of a gamma ray of characteristic energy. This occurs approximately 3 ps after positron emission when the Na decays to Ne. Once inside the polymer material, the positron forms one of the two possible types of positroniums, an ort o-positronium or a p(3 ra-positronium, obtained by pairing with an electron abstracted from the polymer environment. The decay spectra are obtained by the death event of the positron, pi ra-positronium or ort o-positronium species. By appropriate curve fitting, the lifetimes of the various species and their intensity can be determined. The lifetime of an ort o-positronium (Xj) and intensity (I3) have been found to be indicative of the free volume in a polymer system because this is where the relevant species become localised. X3 is related to the size of the free volume sites and I3 to their number concentration. The free volume properties of difunctional and multifunctional epoxies are shown in Table 3.5. The data clearly... 

The prompt gamma-ray cross sections were derived from a comparison of measurements with the neutron beam at the Budapest Reactor and other data from the literature (Molnar 2004 Choi et al. 2007). In some cases, these values were renormalized to better agree with the adopted total radiative cross section from all measurements. Delayed gamma-ray cross sections were derived from a comparison of Budapest Reactor measurements, corrected for activation and decay times, values derived from the ko database, and values adopted from total radiative cross sections and emission probability values from either the Table of Radionuclides (Be et al. 2004) or the ENSDF (2010) nuclear structure and decay database (O Table 36.3). 

Today it is known that other types of radiation, such as neutrons and positrons, are also emitted by radioactive nuclei. However, alpha, beta, and gamma are the most common. I Table 10.1 summarizes the characteristics of these forms. In this book, we usually use the symbol given first for each form the symbols in parentheses are alternatives you might find elsewhere. Except for gamma radiation, which is very high-energy radiation somewhat like X-rays, the radiation emitted by radioactive nuclei consists of streams of particles. The emission of radiation by unstable nuclei is often called radioactive decay. 

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