Nuclear structure

Modem Nuclear Chemistry, by W.D. Loveland, D.J. Morrissey, and G.T. Seaborg Copyright 2006 John Wiley Sons, Inc. 

If we now bring together two nucleons, we find a rather important and interesting fact, only one combination produces a stable (bound) nucleus. One proton and one neutron will combine to form a deuteron, or one hydrogen atom plus one neutron will form a deuterium atom with its atomic electron. Both of the other combinations, two protons that can be labeled 2He and two neutrons, are unbound and come apart almost as rapidly as the constituents come together. It is easy to see that the diproton, or 2He, is more unstable than the dineutron due to the Coulomb repulsion between the two positively charged protons. Thus, we find a preference for equal numbers of neutrons and protons even in the smallest nucleus. 

We can continue our survey of the lightest nuclei with A = 3. Only the combinations of two protons and one neutron, 3He, and one proton with two neutrons, 3H, are bound, while the combinations of three protons, 3Li, and three neutrons are unbound. Again we see a balance between the numbers of neutrons and protons with the extreme cases being unbound. The nuclear spins of both bound A = 3 nuclei are j indicative of a pair of nucleons plus one unpaired nucleon three unpaired nucleons would have had a total spin of. In the A = 3 system the more neutron-rich nucleus, tritium, 3H, is very slightly less stable than 3He and, it decays by (3 emission with a 12.3-y half-life. 

Only one combination of four nucleons is bound, 4He, with two protons and two neutrons. All other combinations of four nucleons are unbound. Moreover, 4He, or the a particle, is especially stable (very strongly bound), and the nucleons are paired to give a total spin 5=0. Interestingly, if we add a nucleon of either type to the a particle, we produce an unbound nucleus Thus, there are no stable nuclei with A = 5 as both 5He and 5Li break apart very rapidly after formation. This creates a gap in the stable masses and poses a problem for the building up of the elements in stars, which is discussed in Chapter 12. There are two bound nuclei with A = 6, 6He and 6Li, with the helium isotope decaying into the lithium isotope, the others are unbound. Continuing on, between mass 6 and 209, all mass numbers 

There exists a pleasing isomorphism between atomic and nuclear structure [21]. In 1937 Wigner pointed out that isospin is the nuclear analogue of ordinary spin. In this view there are two isospin states  

The number of nucleons is denoted by the mass number, A. By analogy to freeon dynamics, the isofreeon states are labeled by Young diagrams with no more than two columns, Li S L2 0 The mass number and the isospin quantum number are then 

The nuclear fermion orbital is product of a spatial (superfreeon) orbital, an ordinary spin (ordspin) orbital and an isospin orbital (which determine the atomic number). In isofreeon dynamics the quantum number, J replaces the ordinary freeon quantum number, L. 

The superfreeon orbitals are taken to be the three-dimensional harmonic oscillator orbitals which lie the following energy sequence 

This energy sequence together with the Gel fand construction leads to the nuclear periodic table 

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H. V. Klapdor, Proceedings of the XXIII Yamada Conference on Nuclear Weak Process and Nuclear Structure, Osaka, Japan, Max Planck Institute fur Kernphysics, Heidelberg, Germany, 1989. 

Atoms with the same value of Zbut different values of A are isotopes (Table 11.1). Many isotopes are stable but others are naturally or artificially radioactive, i.e. their atomic nuclei disintegrate, emitting particles or radiation. This changes the nuclear structure of the atom and often results in the production of a different element. 

All five alkaloids must have the same nuclear structure since lobeline is convertible into lobelanidine by hydrogenation and into lobelanine by oxidation, and worlobelanidine and worlobelanine yield lobelanidine and lobelanine respectively on A-methylation. 

This sub-group includes four alkaloids, a-homochelidonine, chelidonine, chelerythrine, and sanguinarine, whose nuclear structure and interrelationships (formula I to IV) have been established. Three minor chelidonium alkaloids, oxychelidonine, methoxychelidonine and oxy-sanguinarine, whose association is implied by their names, are included. 

This series of ten alkaloids may appropriately be called the cryptopine sub-group, since the characteristic nuclear structure of the type was first made clear by Perkin s investigation of cryptopine. They are closely related to the profoberberines, with which they are interconvertible by two characteristic reactions, which have been of great value in their investigation. The two alkaloids formerly known as )S- and y-homochelidonines have now been renamed a- and -ofiocryptopines respectively to distin-... 

These results justified the nuclear structures (I) and (II) assigned to bebeerine methyl ether and its nitrogen-free degradation product respec-... 

The first indication of the nature of the nuclear structure of yohimbine was seciu-ed by Barger and Field,(1915) who, by distilling the alkaloid with soda-lime, obtained a base, (m.p. 56° picrate, m.p. 157°),... 

Abrine, 484 Abrotine, 772 Abrtis precatorius, 484 Abuta spp., 371 Acacia spp., 771 Acetylcholine, 262, 518 Acetylomithine, 170, 171, 172 Achillea spp., 779 Achilleine achilletine, 779 Acolyctine, 686 Aconine, 673, 675, 679, 685 Aconines, nuclear structure, 693 Aconite alkaloids, 673 Aconitine, 673, 674, 775 oxidation products, 676 Aconitines, pharmacological action, 690 Aconitinone, 676 Aconitoline, 675... 

Kem-. nuclear pithy, choice, -abstand. m. interauclear distance, -anregung, /. nuclear excitation, -aufbau, m. nuclear structure nuclear synthesis, -bewegung, /. nuclear motion. -bildung, /. nucleation. -blndemittel,... 

In the model of nuclear structure you were given in Chapter 6, the nucleus was pictured as being built up of protons and neutrons. These two kinds of particles are given the general name nucleon. The mass number of a nucleus is equal to the number of nucleons present. The superscripts in our equation are mass numbers ... 

A few studies are starting to claim correlations between nuclear structure and electronic configurations such as the occurrence of anomalous configurations in atoms [41-43]. 

I have found that the assumption that in atomic nuclei the nucleons are in large part aggregated into clusters arranged in closest packing leads to simple explanations of many properties of nuclei. Some aspects of the closest-packing theory of nuclear structure are presented in the following paragraphs.1... 

No simple explanation of the onset of deformation at N = 90 has been advanced. I have found that a simple explanation is provided by the close-packed-spheron theory of nuclear structure. 

That stable nuclear structures should involve stable local structures about each of the inner-core spherons is a reasonable consequence of the mutual interdependence of structure and potential energy function and the short range of internucleonic forces. 

During recent decades a great amount of knowledge about the properties of atomic nuclei has been gathered. An extensive theory of nucleonic interactions and nuclear structure [liquid-drop theory (7), shell theory (2, 3), unified theory (4), cluster theory (5—7)] has been developed... 

The proton-neutron ratio in nuclei has been discussed for over 50 years. Long before the neutron had been shown to exist Harkins (17) attempted to draw some conclusions about nuclear structure from the observed excess of neutrons over protons (he used the name neutron for a hypothetical unit of a proton combined with an electron). The course of the proton-neutron ratio is now well understood in relation to the energy change accompanying emission of an electron or positron from the nucleus (that is,... 

The close-packed-spheron theory of nuclear structure may be described as a refinement of the shell model and the liquid-drop model in which the geometric consequences of the effectively constant volumes of nucleons (aggregated into spherons) are taken into consideration. The spherons are assigned to concentric layers (mantle, outer core, inner core, innermost core) with use of a packing equation (Eq. I), and the assignment is related to the principal quantum number of the shell model. The theory has been applied in the discussion of the sequence of subsubshells, magic numbers, the proton-neutron ratio, prolate deformation of nuclei, and symmetric and asymmetric fission. 

Despite the differences in nuclear structures between prokaryotes and eukaryotes, the genetic code, i.e. the combination of bases which does for a particular amino acid in the process of protein synthesis, is the same as it is in all living organisms. 

Angular momentum plays an important role in both classical and quantum mechanics. In isolated classical systems the total angular momentum is a constant of motion. In quantum systems the angular momentum is important in studies of atomic, molecular, and nuclear structure and spectra and in studies of spin in elementary particles and in magnetism. 

LBL. 2000. The Evaluated Nuclear Structure Data File (ENSDF), The National Nuclear Data Center (NNDC). Isotope Explorer version 3.0 bl. Lawrence Berkeley National Laboratory, http //ie.lbl.gov. December 13, 2000. 

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