Isotopic disorder

Isotopic disorders (e.g. in solid chlorine atoms 35C1 and 37C1 isotopes can arise) and nuclear spin degeneracy (ortho and para hydrogen) are two rather less important factors which can also give rise to residual disorder in solids at 0 K. 

Isotopically Mixed Crystals Excitons in LiH Crystals Exciton-Phonon Interaction Isotopic Effect in the Emission Spectrum of Polaritons Isotopic Disordering of Crystal Lattices Future Developments and Applications Conclusions... 

An efficient terminator technique is certainly desirable in the application of recursion methods to the study of disordered systems. It has been shown recently that a self-consistently determined terminator can be fruitfully applied to calculate the electronic states in the Anderson model and to evaluate the vibrational spectrum of lattices with isotopic disorder. The basic idea is to extend the procedures discussed in Section IV to ensemble averages. In this case a useful generalization of Eq. (4.5), satisfied by the terminator t(E), is... 

Ge NMR is subject to great difficulty, and is seldom studied. Recently reported spectra from single crystal germanium with differing isotope contents show quadrupo-lar lineshapes arising from local lattice distortion related to isotopic disorder (Verkhovskii et al. 2000). 

The absorption of H-like centres in semiconductors has been one of my main fields of research. In this volume, I provide a status of their electronic absorption, as known in 2009, and show its evolution from the mid-twentieth century and what this spectroscopy has brought to the understanding of the properties of semiconductors. This evolution has been marked by the improvement of the spectrometer-detector combinations, which have allowed an increase of the spectral resolution by nearly three orders of magnitude, and the production of semiconductor materials like the quasi-monoisotopic crystals, which bring new information on the H-like centres and on the role of isotopic disorder. 

We emphasize first of all that the disorder in the subsurface region, i.e. in the region of localization of the surface exciton, may result from its own internal disorder or may be caused by other, external reasons (e.g. by absorbed molecules). The microscopic surface states under consideration are strongly affected by both types of disorder. This circumstance should be borne in mind even in the cases when SSSE are treated in isotopically disordered crystalline solutions. In such states, which interact weakly with internal crystal monolayers, the effect of internal and external disorder can result in equally serious consequences. We will now make some qualitative remarks on the Anderson localization of surface excitons. As before let us assume a molecular crystal, ignore the exciton-phonon interaction, but take into account, for instance, the diagonal disorder (i.e. the random energy distribution of molecular excitations). 

An extensive discussion of experiments on exciton transport in isotopically disordered crystals and numerical simulations of this phenomenon in the framework of a percolation model may be found in the review paper by Kopel-mann (20). A more recent review of this field, including the discussion of the Anderson model, may be found in the book by Pope and Swenberg (21). 

MHz at room temperature. Due to the small concentration (apprx.0.1%) of the magnetic ( Ge) isotope, the magnetic dipole-dipole interaction is negligible in the samples studied, and the observed specific features of the resonance line shapes (a narrow central peak and a wide plateau) are determined mainly by the quadrupole interaction of magnetic nuclei with the random electric-field gradient (EFG) induced by the isotopic disorder. 

In general, the specific information that can be obtained from a simple solid state NMR experiment depends on the personality of the nuclear isotope under study. In many cases, solid state NMR spectra are not as straightforwardly interpretable as in the preceding example. Furthermore, disordered materials, such as thin films. 

Let us fix attention on a particular H20 molecule A in the interior of water (if we wish to identify this molecule we can suppose that it contains a nucleus of the oxygen isotope 01S) and let us consider the water molecules which happen to be nearest neighbors of this molecule at the moment. These molecules have been in contact with A for different lengths of time. Since all the molecules in the liquid wander about, there was a time when none of these molecules was in contact with A. Further, if we could now begin to watch these molecules, we should find that, after the lapse of different periods of time, they become separated from A and each is replaced by another molecule. Similar remarks can be made about the molecules which come into contact with any chosen molecule. We can now raise the question—-What is the rate of turnover of this process The rate depends on the degree of local order and disorder, which in turn depends on the strength and character of the forces between adjacent molecules. 

The crystallographic study of the potassium salt is complicated by disorder but in CsOs03N Os=N is 1.676 A and Os=0 1.739-1.741 A. Assignments of the vibrational spectrum of Os03N is assisted by isotopic substitution the higher frequency absorption is shifted significantly on 15N substitution whereas the band just below 900 cm-1 is scarcely affected (Table 1.7) conversely the latter band is shifted by some 50 cm-1 on replacing l60 by l80 [56], Nitrido salts are discussed later (section 1.12.2). 

X lO kJ/mol. If a patient with a th Toid disorder is given this isotope and 7.45 pg is incorporated into the thyroid gland, how much energy will the gland receive in one day ... 

Itou, T., Teramoto, A., Matsuo, T., and Suga, H., Isotope effect on the order-disorder transition in aqueous schizophyllan, Carbohydr. Res., 160, 243, 1987. 

Lithium is an important element in many industries (Bach 1985). Lithium is used medically as a treatment for bipolar disorders (Schou 1988). Lithium toxicity, especially to the renal system, is problematical. Estimating systemic elemental mass balance, especially for patients receiving oral Li dosing, is important, and is one area in which Li isotope ratios are... 

Stoll PM, Stokes PE, Okamoto M (2001) Lifiiium isotopes differential effects on renal fimction and histology. Bipolar Disorders 3 174-180... 

The formation of l from 1 had been postulated by Vetter [8a]. From the above information we can make the following conclusions (a) l" (atom-free radical) can be produced electrochemically, (b) l" does react with pyridine and may react with similar compounds and (c) recombination of l" may be slow in solution phase. Molecular iodine (di-iodine) the radio-isotope, is being used in the treatment of thyroid disorder. One can ask the question is there any biologically beneficial or toxic effect of iodine atom. There has been no study [8b]. 

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