scholarly journals Paramagnetische Elektronenresonanz thermisch und durch Strahlung erzeugter Zentren in Bornitrid

1966 ◽  
Vol 21 (11) ◽  
pp. 1970-1975 ◽  
Author(s):  
G. Römelt
Keyword(s):  
Isotopic Composition ◽  
Line Width ◽  
Line Shape ◽  
X Rays ◽  
Natural Isotopic Composition ◽  
Epr Spectrum ◽  
Γ Radiation ◽  
Impurity Atoms ◽  
Gaussian Line Shape ◽  
Gaussian Line

By X-rays, ultraviolet, and γ-radiation or by heating to more than 1850 °C in powdered or sintered boronnitride centres are produced, which give an EPR-spectrum with 10 lines a=7.8 ± 0.1 Gauss apart with g=2.0027 ± 0.0003 for BN of natural isotopic composition (81.17% 11B; 18.83% 10B), and a single line for 10BN enriched to 91% 10B. The spectra are analysed as built up from 4 systems of spectra, caused by surroundings of 3 boron atoms, 3, 2, 1, or 0 of which are 11B, each occuring with the proper probability. The intensity of the different systems was calculated by assuming GAussian line shape and equal | ψ (0) |2 and line width for 11B and 10B. It is possible, that the EPR is caused by impurity atoms on the places of N or in the centre of B3N3-rings. Other spectra caused in BN by X-rays or by neutrons in a pile are discussed elsewhere 3, 8.

An Attempt to Incorporate the Gaussian Line Shape in the Study of Spectroscopic Limiting Line Intensity

1988 ◽  
Vol 42 (5) ◽  
pp. 729-730 ◽  
Author(s):  
C. T. Yap ◽  
I. V. Anion
Keyword(s):  
Spectral Line ◽  
Line Intensity ◽  
Line Shape ◽  
Experimental Situation ◽  
Photon Counting ◽  
Detection Limits ◽  
Statistical Precision ◽  
Gaussian Line Shape ◽  
Gaussian Line

We approach the problem of detection limits in particle or photon counting spectroscopies by looking at both the intensity and the shape of the spectral line instead of looking only at the background under the line. We develop a method by which, for a given experimental situation in which the background height and FWHM are known, and at a given statistical precision, we obtain a uniquely defined limiting line intensity.

Radiation Effects on Hollandite Ceramics developed for Radioactive Cesium Immobilization

2003 ◽  
Vol 792 ◽  
Author(s):  
V. Aubin ◽  
D. Caurant ◽  
D. Gourier ◽  
N. Baffier ◽  
S. Esnouf ◽  
...  
Keyword(s):  
Radiation Effects ◽  
Liquid Waste ◽  
Fission Products ◽  
Radioactive Cesium ◽  
Radioactive Liquid Waste ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Γ Radiation ◽  
The Stability ◽  
High Level

ABSTRACTProgress on separating the long-lived fission products from the high level radioactive liquid waste (HLW) has led to the development of specific host matrices, notably for the immobilization of cesium. Hollandite (nominally BaAl2Ti6O16), one of the main phases constituting Synroc, receives renewed interest as specific Cs-host wasteform. The radioactive cesium isotopes consist of short-lived Cs and Cs of high activities and Cs with long lifetime, all decaying according to Cs+→Ba2++e- (β) + γ. Therefore, Cs-host forms must be both heat and (β,γ)-radiation resistant. The purpose of this study is to estimate the stability of single phase hollandite under external β and γ radiation, simulating the decay of Cs. A hollandite ceramic of simple composition (Ba1.16Al2.32Ti5.68O16) was essentially irradiated by 1 and 2.5 MeV electrons with different fluences to simulate the β particles emitted by cesium. The generation of point defects was then followed by Electron Paramagnetic Resonance (EPR). All these electron irradiations generated defects of the same nature (oxygen centers and Ti3+ ions) but in different proportions varying with electron energy and fluence. The annealing of irradiated samples lead to the disappearance of the latter defects but gave rise to two other types of defects (aggregates of light elements and titanyl ions). It is necessary to heat at relatively high temperature (T=800°C) to recover an EPR spectrum similar to that of the pristine material. The stability of hollandite phase under radioactive cesium irradiation during the waste storage is discussed.

scholarly journals Can gravitational microlensing be used to probe geometry of a massive black-hole?

2006 ◽  
Vol 2 (S238) ◽  
pp. 431-432
Author(s):  
Luka Č Popović ◽  
Predrag Jovanović
Keyword(s):  
Black Hole ◽  
Line Shape ◽  
X Rays ◽  
Massive Black Hole ◽  
Gravitational Microlensing ◽  
Probe Geometry

AbstractHere we discuss the possibility to use gravitational microlensing in order to probe the geometry around a massive black hole. Taking into account that lensed quasars are emitting X-rays which come from the heart of these objects, we investigated the influence of microlensing on the Fe Kα line shape originated in Schwarzschild and Kerr metrics.

The electrical resistivity of lithium-6

1961 ◽  
Vol 263 (1314) ◽  
pp. 407-419 ◽  
Keyword(s):  
Electrical Resistivity ◽  
Isotopic Composition ◽  
Specific Heat ◽  
Room Temperature ◽  
Natural Isotopic Composition ◽  
Square Roots ◽  
Conduction Electrons ◽  
Ionic Mass ◽  
Theoretical Predictions ◽  
Electrical Resistivities

The electrical resistivities of lithium -6 and lithium of natural isotopic composition have been studied between 4°K and room temperature. In addition, their absolute resistivities have been carefully compared at room temperature. These measurements show that the effect of ionic mass on electrical resistivity agrees with simple theoretical predictions, namely, that the properties of the conduction electrons in lithium do not depend on the mass of the ions, and that the characteristic lattice frequencies for the two pure isotopes are in the inverse ratio of the square roots of their ionic masses. A comparison with the specific heat results of Martin (1959, 1960), where the simple theory is found not to hold, indicates the possibility that anharmonic effects are present which affect the specific heat but not the electrical resistivity.

scholarly journals Magnetic properties of the natural and isotope-modified diamond and silicon carbide

2018 ◽  
Vol 185 ◽  
pp. 04007 ◽  
Author(s):  
A.N. Taldenkov ◽  
A.V. Inyushkin ◽  
E.A. Chistotina ◽  
V.G. Ralchenko ◽  
A.P. Bolshakov ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Magnetic Properties ◽  
Isotopic Composition ◽  
Single Crystals ◽  
High Purity ◽  
Diamagnetic Susceptibility ◽  
Synthetic Diamond ◽  
Paramagnetic Centers ◽  
Natural Isotopic Composition ◽  
Ferromagnetic Component

The magnetic properties of single crystals of synthetic diamond and crystals of silicon carbide were studied. High-purity samples of diamonds synthesized with HPHT and CVD technologies were used. The crystals of silicon carbide were grown by sublimation and industrial technology. Along with samples with a natural isotopic composition, monoisotopic crystals of diamond (99.96% 12C and 99.96% 13C) and silicon carbide (99.993% of 28Si) were studied. On the basis of the data obtained, the diamagnetic susceptibility was determined and the concentration of paramagnetic centers and the content of the ferromagnetic component were evaluated. The results are discussed.

scholarly journals The absorption of hard monochromatic γ-radiation

1930 ◽  
Vol 128 (807) ◽  
pp. 345-359 ◽  
Keyword(s):  
Absorption Coefficient ◽  
High Frequency ◽  
Wave Length ◽  
Low Frequency ◽  
Photoelectric Effect ◽  
Fourth Power ◽  
X Rays ◽  
Photoelectric Absorption ◽  
Initial Direction ◽  
Γ Radiation

Energy may be removed from a beam of γ -rays traversing matter by two distinct mechanisms. A quantum of radiation may be scattered by an electron out of its initial direction with change of wave-length, or it may be absorbed completely by an atom and produce a photoelectron. The total absorption coefficient, μ, is defined by the equation d I/ dx = -μI, and is the sum of the coefficients σ and τ referring respectively to the scattering and to the photoelectric effect. For radiation of low frequency, such as X-rays, the photoelectric absorption is very much more important than the absorption due to scattering, and many experiments have shown that the photoelectric absorption per atom varies as the fourth power of the atomic number and approximately as the cube of the wave-length. For radiation of high frequency, such as the more penetrating γ -rays, the photoelectric effect is, even for the heavy elements, smaller than the scattering absorption; and, since the scattering from each electron is always assumed to be independent of the atom from which it is derived, it is most convenient to divide μ. defined above by the number of electrons per unit volume in the material and to obtain μ e the absorption coefficient per electron.

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