Role of Non-Radiative Transitions in X-RAY Analysis

Author(s):  
János L. Lábár

Radiative and non-radiative transitions present alternative ways for the excited atom to reduce its energy when the initial state is an atom singly ionised in one of its inner electron shells. Since the fluorescence yield gives the probability that the empty state in the inner (sub)shell is filled in by a radiative process, it seems that the generated x-ray intensities are independent of the non-radiative rearrangements from the point on where the value of fluorescence yield is given for the (sub)shell in question. In that way the intensity of an x-ray line would solely be dependent on the ionisation probability of the given (sub)shell and on the rates of the radiative transitions (determining the relative intensities of the lines originating from the same subshell). That image involves that the non-radiative processes only influence the value of the fluorescence yield. For the simplest case i.e. for the K shell it is true.

2004 ◽  
Vol 19 (9) ◽  
pp. 2699-2702 ◽  
Author(s):  
C.S. Zhang ◽  
H.B Xiao ◽  
Y.J. Wang ◽  
Z.J. Chen ◽  
X.L. Cheng ◽  
...  

Erbium and silicon were dual implanted into thermally grown SiO2 film on Si (110) substrates, followed by thermal treatment at 700–1200 °C for 30 min. The microstructure was studied by transmission electron microscope and x-ray diffraction. When the implanted films were annealed at T > 900 °C, the silicon nanocrystals (nc-Si) enwrapped by amorphous silicon (a-Si) could be observed. The thermal quenching behavior at λ = 1.535 μm and its relation with the annealling temperature were also investigated. With increasing annealing temperature, the portion of a-Si and the thermal quenching both decreased. Efficient luminescence from Er ions and weak intensity thermal quenching were obtained from the sample annealed at 1100 °C. The role of a-Si in non-radiative processes at T > 100 K is discussed.


2015 ◽  
Vol 93 (2) ◽  
pp. 218-226 ◽  
Author(s):  
T.K. Sham ◽  
R.A. Gordon

We report recent observations of resonant inelastic X-ray scattering (RIXS) at the cerium L3-edge of CePO4, CeO2, and Ce3+ ion in aqueous solution. The intensity of the emission spectrum, including the dispersive Raman below the edge and the emerging nondispersive fluorescence above the edge, was recorded with a solid-state detector with low-energy resolution and a WDX detector with modestly high-energy resolution. The yield of the emission was used to monitor the cerium L3-edge X-ray absorption near edge structures (XANES) in a constant initial state (CIS) mode as the photon energy sweeps across the cerium L3-edge. The CIS XANES is compared with the XANES recorded using the nondispersive fluorescence yield, Lα, in a constant final state (CFI) mode. It is found that the Raman yield dominates the total emission in the pre-edge region and diminishes rapidly at threshold. The RIXS of Ce3+ in aqueous solution exhibits similar behavior as CePO4. The post-whiteline RIXS intensity of CePO4 exhibits a correlation with excitation energy. CeO2 also exhibits a less intense whiteline in CIS XANES compared with the XANES detected with normal fluorescence. The implications of these observations with improved instrumental resolution are noted.


Author(s):  
L. T. Germinario

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.


Author(s):  
Janet H. Woodward ◽  
D. E. Akin

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.


Author(s):  
K. Teraoka ◽  
N. Kaneko ◽  
Y. Horikawa ◽  
T. Uchida ◽  
R. Matsuda ◽  
...  
Keyword(s):  

The aim of this study was to elucidate the role of the mitochondria as a store of calcium(Ca) under the condition of pathophysiological Ca overload induced by a rise in extracellular Ca concentration and the administration of isoproterenol.Eight rats were employed, and hearts were perfused as in the Langendorff method with Krebs-Henseleit solution gassed with 95% O2 and 5% CO2. Tow specimens were perfused with 2mM Ca for 30 min, and 2 were perfused with 5.5 mM Ca for 20 min. 4 specimens were perfused with 2 mM Ca for 5 min, and of these 4, 2 were infused with 10-7 mM/kg/min. isoproterenol for 5 min, and 2 were given a bolus injection of 3 x 10-7 mM isoproterenol. After rapid-cryofixation by the metal-mirror contact method with a Reichert-Jung KF80/MM80, and cryosectioning at -160 to -180° C with a Reichert-Jung Ultracut Fc-4E, ultrathin specimens (100nm) were free-ze-dreid for several hours at 10-5 Torr in the JEOL FD 7000, and mitochondrial Ca was determined by quantitative x-ray micranalysis (JEOL 1200EX, LINK AN 10000S).


Author(s):  
Ann LeFurgey ◽  
Peter Ingram ◽  
J.J. Blum ◽  
M.C. Carney ◽  
L.A. Hawkey ◽  
...  

Subcellular compartments commonly identified and analyzed by high resolution electron probe x-ray microanalysis (EPXMA) include mitochondria, cytoplasm and endoplasmic or sarcoplasmic reticulum. These organelles and cell regions are of primary importance in regulation of cell ionic homeostasis. Correlative structural-functional studies, based on the static probe method of EPXMA combined with biochemical and electrophysiological techniques, have focused on the role of these organelles, for example, in maintaining cell calcium homeostasis or in control of excitation-contraction coupling. New methods of real time quantitative x-ray imaging permit simultaneous examination of multiple cell compartments, especially those areas for which both membrane transport properties and element content are less well defined, e.g. nuclei including euchromatin and heterochromatin, lysosomes, mucous granules, storage vacuoles, microvilli. Investigations currently in progress have examined the role of Zn-containing polyphosphate vacuoles in the metabolism of Leishmania major, the distribution of Na, K, S and other elements during anoxia in kidney cell nuclel and lysosomes; the content and distribution of S and Ca in mucous granules of cystic fibrosis (CF) nasal epithelia; the uptake of cationic probes by mltochondria in cultured heart ceils; and the junctional sarcoplasmic retlculum (JSR) in frog skeletal muscle.


Author(s):  
Judith A. Murphy ◽  
Anthony Paparo ◽  
Richard Sparks

Fingernail clams (Muscu1ium transversum) are dominant bottom-dwelling animals in some waters of the midwest U.S. These organisms are key links in food chains leading from nutrients in water and mud to fish and ducks which are utilized by man. In the mid-1950’s, fingernail clams disappeared from a 100-mile section of the Illinois R., a tributary of the Mississippi R. Some factor(s) in the river and/or sediment currently prevent clams from recolonizing areas where they were formerly abundant. Recently, clams developed shell deformities and died without reproducing. The greatest mortality and highest incidence of shell deformities appeared in test chambers containing the highest proportion of river water to well water. The molluscan shell consists of CaCO3, and the tissue concerned in its secretion is the mantle. The source of the carbonate is probably from metabolic CO2 and the maintenance of ionized Ca concentration in the mantle is controlled by carbonic anhydrase. The Ca is stored in extracellular concentric spherical granules(0.6-5.5μm) which represent a large amount of inertCa in the mantle. The purpose of this investigation was to examine the role of raw river water and well water on shell formation in the fingernail clam.


Author(s):  
Ирина Викторовна Евстафьева

В статье исследуются вопросы попечительства в отношении несовершеннолетних, отбывающих наказание в виде лишения свободы. Проблема, поднимаемая автором настоящей статьи, многогранна, касается различных аспектов отбывания наказания несовершеннолетними в воспитательных колониях и требует комплексного исследования, способного ответить на определенно значимый вопрос: является ли колония законным представителем находящихся в ней несовершеннолетних со всеми вытекающими из статуса законных представителей последствиями. При этом необходимо обращать внимание на специфику правового статуса лиц, отбывающих наказание в воспитательных колониях, которые, во-первых, являются несовершеннолетними, то есть не обладают дееспособностью в полном объеме и нуждаются в особой заботе, защите и представительстве, а во-вторых, осуждены за совершение тяжкого или особо тяжкого преступления, влекущего изоляцию от общества и определенные ограничения и лишения. Отечественное законодательство достаточно детально регламентирует особенности режима отбывания наказания в виде лишения свободы несовершеннолетними, не определяя при этом статуса воспитательных колоний, кем они являются: воспитателями, попечителями или исключительно учреждениями исполнения наказаний. Между тем правильное понимание значения и роли воспитательной колонии в жизни находящихся в ней несовершеннолетних преступников, по мнению автора, поможет избежать ряда проблем, объективно складывающихся в учреждениях подобного рода. С этой точки зрения предлагаемая тема представляет интерес не только для ученых-теоретиков, но и для практиков - сотрудников соответствующих учреждений. Особо следует подчеркнуть, что исследований по данной тематике в специальной литературе нет. Отдельные исследования, встречающиеся в современной литературе, касаются исключительно общего гражданско-правового статуса несовершеннолетних осужденных. Однако это обстоятельство может свидетельствовать только о новизне данной темы, но никак не об отсутствии самой проблемы. The article analyzes the issues of the status of educational colonies as guardians of minors serving a sentence of imprisonment. In fact, the problem raised by the author of this article is multifaceted, concerns various aspects of the serving of punishment by minors in educational colonies and requires a comprehensive study that can answer, it seems, a definitely significant question: whether the colony is the legal representative of the minors in it with all the consequences arising from the status of legal representatives in the form of duties and responsibilities. At the same time, it seems, it is necessary to pay attention to the specifics of the legal status of citizens serving sentences in educational colonies, who, firstly, are minors, i.e. do not have full legal capacity and need special care, protection and representation, and, secondly, are convicted of committing a serious or particularly serious crime, entailing isolation from society and certain restrictions and deprivation. Domestic legislation regulates in sufficient detail the peculiarities of the regime of serving sentences in the form of deprivation of liberty by minors, without determining the status of educational colonies. Who are they: educators, Trustees or only institutions of execution of punishments. Meanwhile, the correct understanding of the importance and role of the educational colony in the life of juvenile offenders in it, according to the author, will help to avoid a number of problems that objectively develop in institutions of this kind. From this point of view, the proposed topic is of interest not only for theoretical scientists, but for practitioners-employees of relevant institutions. It should be emphasized that there are no studies on this subject in the special literature. However, this circumstance can testify only about novelty of the given subject, but in any way about absence of the problem. It seems that the relevance and importance of a problem is not always measured by the number of studies devoted to it. Sometimes these its traits are manifest only under particularly careful consideration.


1993 ◽  
Vol 58 (7) ◽  
pp. 1591-1599 ◽  
Author(s):  
Abd El-Aziz A. Said

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.


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