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Lithium nuclear distribution

Important information is included in the anisotropic atomic displacement parameters for lithium, which determine the overall anisotropy of the thermal vibration by the shape of ellipsoid. Green ellipsoids shown in Figs. 14.11a, c and 13 represent the refined lithium vibration. The preferable direction of fhennal displacement is toward the face-shared vacant tetrahedra. The expected curved one-dimensional continuous chain of lithium atoms is drawn in Fig. 14.13 and is consistent with the computational prediction by Morgan et al. [22] and Islam et al. [23]. Such anisotropic thermal vibratiOTis of lithium were further supported by the Fourier synthesis of the model-independent nuclear distribution of lithium (see Fig. 14.14). [Pg.463]

A three-dimensional contour surface (0.15 fin A ) of nuclear distribution of lithium atoms is shown in Fig. 14.17. The probability density of lithium nuclei strictly distributes into the continuous curved one-dimensional chain along the [010] direction, which is consistent with the computational predictions by Morgan et al. [22] and Islam et al. [23]. Other atoms, Fe, P, and O remained to be localized at the initial positions even after MEM analysis. Given the two possible diffusion paths in Fig. 14.11, the microscopic reason of the diffusimi anisotropy can be the difference... [Pg.467]

As the weak interaction is the slowest of all, it was the first to find itself unable to keep up with the rapid expansion of the Universe. The neutrinos it produces, which serve as an indicator of the weak interaction, were the first to experience decoupling, the particle equivalent of social exclusion. By the first second, expansion-cooled neutrinos ceased to interact with other matter in the form of protons and neutrons. This left the latter free to organise themselves into nuclei. Indeed, fertile reactions soon got under way between protons and neutrons. However, the instability of species with atomic masses between 5 and 8 quickly put paid to this first attempt at nuclear architecture. The two species of nucleon, protons and neutrons, were distributed over a narrow range of nuclei from hydrogen to lithium-7, but in a quite unequal way. [Pg.204]

We have also performed the calculation of hyperfine coupling constants the electric quadrupole constant B and magnetic dipole constant A, with inclusion of nuclear finiteness and the Uehling potential for Li-like ions. Analogous calculations of the constant A for ns states of hydrogen-, lithium- and sodiumlike ions were made in refs [11, 22]. In those papers other bases were used for the relativistic orbitals, another model was adopted for the charge distribution in the nuclei, and another method of numerical calculation was used for the Uehling potential. [Pg.297]

Mechanisms and rates of transport of nuclear test debris in the upper and lower atmosphere are considered. For the lower thermosphere vertical eddy diffusion coefficients of 3-6 X 106 cm.2 sec. 1 are estimated from twilight lithium enhancement observations. Radiochemical evidence for samples from 23 to 37 km. altitude at 31° N indicate pole-ward mean motion in this layer. Large increases in stratospheric debris in the southern hemisphere in 1963 and 1964 are attributed to debris from Soviet tests, transported via the mesosphere and the Antarctic stratosphere. Most of the carbon-14 remains behind in the Arctic stratosphere. 210Bi/ 210Pb ratios indicate aerosol residence times of only a few days at tropospheric levels and only several weeks in the lower stratosphere. Implications for the inventory and distribution of radioactive fallout are discussed. [Pg.146]

A more common technique employs a nuclear emulsion to detect the radiation. The sample is irradiated in close proximity to a sensitive emulsion, which is subsequently developed, fixed, and examined under the microscope. In this way it is possible to distinguish tracks due to alpha particles, fission fragments, etc. Faraggi et al. 22) and Mayr 54) used this technique to determine boron by the B (n,a)Lr reaction down to a level of 2 X 10" gm. Lithium at the 10" -gm level was determined by Picciotto and van Styvendael 69) by the reaction Li (n.,a)H and Curie and Faraggi 18) studied the distribution of uranium in the surface of polished mineral specimens by the U (n,/) reaction. [Pg.328]

The composition of the Earth was determined both by the chemical composition of the solar nebula, from which the Sun and planets formed, and by the nature of the physical processes that concentrated materials to form planets. The bulk elemental and isotopic composition of the nebula is believed or usually assumed to be identical to that of the Sun. The few exceptions to this include elements and isotopes such as lithium and deuterium that are destroyed in the bulk of the Sun s interior by nuclear reactions. The composition of the Sun as determined by optical spectroscopy is similar to the majority of stars in our galaxy and, accordingly, the relative abundances of elements in the Sun are referred to as "cosmic abundances". Although the cosmic abundance pattern is commonly seen in other stars, there are dramatic exceptions, such as stars composed of iron or solid nuclear matter, as is the case with neutron stars. The best estimation of solar abundances is based on data from optical spectroscopy and meteorite studies and in some cases extrapolation and nuclear theory. The measured solar abundances are listed in Fig. 2-1 and Table 2-1. It is believed to be accurate to about 10% for the majority of elements. The major features of the solar abundance distribution are a strong decrease in the abundance of heavier elements, a large deficiency of Li, Be, and B, and a broad abundance peak centered near Fe. The factor of 10 higher... [Pg.9]

The first analysis performed for the Lio,6FeP04 solid-solution phase at 620 K was the Rietveld refinement for the neutron diffraction profile and the resultant pattern is summarized in Fig. 14.12b. To evaluate the dynamic disorder of lithium, maximum entropy method (MEM) was applied to estimate the neutron scattering length density distribution, which corresponds to the nuclear density distribution. [Pg.464]

Fig. 14.14 The 010 plane slice of difference Fourier scattering length density plot of LiFeP04 with contours in 0.05 fin steps. The map was calculated by Fo(Li) = Fo( LiFeP04) - caic.(LioFeP04), where F and Fcaic. ste the observed and calculated structure factors, respectively, and LioFeP04 expresses the FeP04 framework having identical structural parameters with LiFeP04. The nuclear density distribution of lithium itself is anisotropic with the same direction as the refined thermal vibration... Fig. 14.14 The 010 plane slice of difference Fourier scattering length density plot of LiFeP04 with contours in 0.05 fin steps. The map was calculated by Fo(Li) = Fo( LiFeP04) - caic.(LioFeP04), where F and Fcaic. ste the observed and calculated structure factors, respectively, and LioFeP04 expresses the FeP04 framework having identical structural parameters with LiFeP04. The nuclear density distribution of lithium itself is anisotropic with the same direction as the refined thermal vibration...

See other pages where Lithium nuclear distribution is mentioned: [Pg.467]    [Pg.261]    [Pg.399]    [Pg.138]    [Pg.334]    [Pg.173]    [Pg.1690]    [Pg.43]    [Pg.43]    [Pg.215]    [Pg.126]    [Pg.93]    [Pg.57]    [Pg.58]    [Pg.73]    [Pg.22]    [Pg.12]    [Pg.238]    [Pg.313]    [Pg.285]    [Pg.238]    [Pg.828]    [Pg.765]    [Pg.187]    [Pg.315]    [Pg.208]    [Pg.361]    [Pg.142]    [Pg.666]   
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Lithium distribution

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