Nuclides isomers

Not known whether ground-state nuclide, isomer, or identification error. 

Isomers—Nuclides having the same number of neutrons and protons but capable of existing, for a measurable time, in different quantum states with different energies and radioactive properties. Commonly the isomer of higher energy decays to one with lower energy by the process of isomeric transition. 

Nuclide—A species of atom characterized by the constitution of its nucleus. The nuclear constitution is specified by the number of protons (Z), number of neutrons (N), and energy content or, alternatively, by the atomic number (Z), mass number A (N+Z), and atomic mass. To be regarded as a distinct nuclide, the atom must be capable of existing for a measurable time. Thus, nuclear isomers are separate nuclides, whereas promptly decaying excited nuclear states and unstable intermediates in nuclear reactions are not so considered. 

Mossbauer isomer shift and quadrupole splitting are commonly used to obtain information about the bonding environment around source nuclides. The isomer shift arises from the electric monopole interaction of the nucleus with the electrons and depends on the... 

The second problem in relation to Mossbauer spectroscopy, which is trivial but irksome, is agreeing on a reference point with respect to isomer shifts. Each particular nuclide has several possible chemical environments for the source and therefore several possible reference... 

Since the discovery of the first spontaneously fissioning isomer, a number of other examples have been found. The positions of these nuclei in the chart of nuclides are... 

Figure 11.6 Position of the known spontaneously fissioning isomers in the nuclide chart. (Figure also appears in color figure section.)...

Nuclides are listed in order of increasing atomic number (Z), and are subordered by increasing mass number (A). All isotopic species, as well as all isomers with half-life >0.1 s, and some with half-life>l ms which decay by SF, a or p emissions, are included. A nuclide is given even if only its mass estimate or its... 

Figure 11.6 Position of the known spontaneously fissioning isomers in the nuclide chart.

Nuclide. Each nuclide is identified by its atomic number Z, equal to the number of protons in the nucleus the corresponding symbol for that element and the mass number A, equal to the sum of the numbers of protons Z and neutrons N in the nucleus. Thus, A = Z + N, or N = A — Z. The m following the mass number (e.g., 69mZn) indicates an isomer of that nuclide. 

TABLE 21.1 Definitions of Atoms, Chemical Elements, Isotopes, Nuclides, and Isomers... 

Isomers Nuclides with the same numbers of protons and neutron but in different energy states. 

For certain nuclides, different physical properties (half-lives, mode of decay) are observed. They are due to different energetic states, the ground state and one or more metastable excited states of the same nuclide. These different states are called isomers or nuclear isomers. Because the transition from the metastable excited states to the ground states is forbidden , they have their own half-lives, which vary between some milliseconds and many years. The excited states (isomers) either change to the ground state by emission of a y-ray photon (isomeric transition IT) or transmutation to other nuclides by emission of cc or particles. Metastable excited states (isomers) are characterized by the suffix m behind the mass number A, for instance Co and Co. Sometimes the ground state is indicated by the suffix g. About 400 nuclides are known to exist in metastable states. 

Szilard-Chalmers reactions are of special interest for the investigation of nuclear isomers, because they offer the possibility of separating isomeric nuclides. 

Nuclides (i.e. kinds of atomic nuclei) having the same atomic and mass numbers, but existing in different energy states. One is always unstable with respect to the other, or both may be unstable with respect to a third. In the latter instance the energy of transformation in the two cases will differ. See geometric isomer optical isomer. 

Isomers. Nuclides having the same atomic and mass numbers but differing in energy and spin of the nuclei. For example, "Tc and "mTc are isomers. 

All homonuclear diatomic molecules having nuclides with non-zero spin are expected to show nuclear spin isomers. The effect was first detected in dihydrogen where it is particularly noticeable, and it has also been established for D2, T2, N2, N2, Oj, etc. When the two nuclear spins are parallel (ort/jo-hydrogen) the resultant nuclear spin quantum number is 1 (i.e. 5 -b j) and the state is threefold degenerate (2S -(-... 

In an (n, 7) reaction in which the product nuclide is in an isomeric state, the column Prod. lists the designation of the isomer. For example, the reaction... 

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