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    Tytuł:
    X-Ray Absorption Spectroscopy
    Autorzy:
    Mobilio, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1931690.pdf
    Data publikacji:
    1994-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    07.85.+n
    78.70.Dm
    Opis:
    X-ray absorption spectroscopy, today widely used as a tool for structural investigations, is described. Theoretically it is shown that above an absorption edge the absorption coefficient is well approximated by a sum of terms, each one describing a particular path followed by the photoelectron outgoing from the atom. Such geometrical feature allows to use X-ray absorption spectroscopy for structural investigations. The data analysis procedures are outlined. Applications of the single scattering region, generally known as EXAFS to semiconductors alloys, to metallic clusters and to the crystallization of amorphous metallic glasses are illustrated. Multiple scattering calculations and their relation to experimental spectra is discussed in the case of Mn ions in solution. Application of the multiple scattering to determine the three-body correlation function in a-Si:H is shown.
    Źródło:
    Acta Physica Polonica A; 1994, 86, 5; 645-661
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Cavity Enhanced Absorption Spectroscopy Sensor
    Autorzy:
    Nowakowski, M.
    Wojtas, J.
    Bielecki, Z.
    Mikołajczyk, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1807740.pdf
    Data publikacji:
    2009-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    07.50.Qx
    42.79.Sz
    43.60.-c
    07.07.Df
    Opis:
    The paper presents opportunities of cavity enhanced absorption spectroscopy technique application in nitrogen oxides (NO_{x}) detection. In this method the concentration of an absorbing gas is determined by measure of decay time of the light pulse trapped in an optical cavity. The measurements are not sensitive to fluctuation of both laser power and photodetector sensitivity. The cavity enhanced absorption spectroscopy technique is a modification of cavity ring down spectroscopy technique where the off-axis adjustment of the resonator is used. NO_{x} detection is carried out in the visible and infrared range. The signal is registered with a developed low noise photoreceiver. Features of the presented sensor show that it is possible to build a portable trace gases sensor. Its sensitivity could be comparable with chemical detectors. Such a system has several advantages: relatively low price, small size and weight, and detection possibility of other gases.
    Źródło:
    Acta Physica Polonica A; 2009, 116, 3; 363-367
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Surface X-Ray Absorption Spectroscopy: Basic Concepts and Applications
    Autorzy:
    Lagarde, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1963303.pdf
    Data publikacji:
    1997-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    68.35.Gy
    78.70.Dm
    Opis:
    The application to surface problems of X-ray spectroscopy has started almost at the same time as in materials science. While the theoretical basis is obviously the same, SEXAFS has some experimental peculiarities which are reviewed here. Some examples will then be given.
    Źródło:
    Acta Physica Polonica A; 1997, 91, 4; 641-647
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Two-Channel Optoelectronic Sensor Employing Cavity Enhanced Absorption Spectroscopy
    Autorzy:
    Wojtas, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1493278.pdf
    Data publikacji:
    2011-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    07.07.Df
    42.25.Dd
    42.55.Px
    42.60.Da
    42.62.Fi
    Opis:
    In the paper, a description of two-channel of optoelectronic sensor basing on cavity enhanced absorption spectroscopy is presented. In contrast to the typical cavity enhanced absorption spectroscopy systems, here a special optical system is applied. It provides possibility to direct more than one beam of laser radiation into a cavity. Thus, special lasers controller system and photoreceiver were developed as well. The setup includes two pulsed laser diodes. The optical signals from the lasers are registered with one special constructed photoreceiver, which is characterized by wide range of the detected wavelengths. Moreover, there was applied time division multiplexing technique, well-known in the telecommunication systems. Every laser is assigned to the suitable channel - the strictly determined temporary window. In this window, the signal from the exits of the optical cavity is registered. In the system, optical signal from many laser sources can be measured and value of absorption coefficient at a few different wavelengths can be determined parallel. Typical cavity enhanced absorption spectroscopy system is designed to measure only one gas concentration, while the developed setup provides possibility to detect a trace concentration of two gases at the same time.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 4; 763-766
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Calorimetric Absorption Spectroscopy of Deep Defects and Quantum Dots
    Autorzy:
    Heitz, R.
    Podlowski, L.
    Böhrer, J.
    Hoffmann, A.
    Broser, I.
    Bimberg, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/1933692.pdf
    Data publikacji:
    1995-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.55.Eq
    73.20.Dx
    71.70.Gm
    Opis:
    In recent years calorimetric absorption spectroscopy has been developed to a powerful tool of semiconductor spectroscopy based on the detection of nonradiative relaxation processes. Calorimetric absorption spectroscopy is an ultrasensitive quantitative absorption technique. Recent investigations of Fe in III-V semiconductors and of InAs/GaAs quantum dots are presented here to illustrate the potential of the method. Sharp absorption lines are observed at the low energy onset of the Fe $\text{}^{3+}\text{}^{/}\text{}^{2+}$ charge transfer band in III-V semiconductors. Calorimetric absorption spectroscopy measurements in the mK range reveal a strong temperature dependence of their absorption strength identifying unambiguously Fe$\text{}^{3+}$($\text{}^{6}$A$\text{}_{1}$(S)) as a ground state. The excited state is attributed to (Fe$\text{}^{2+}$,h). The importance of exchange interaction for the observed fine structure is pointed out and binding energies are determined. The quantum yield of the intracenter $\text{}^{5}$Τ$\text{}_{2}$-$\text{}^{5}$E transition of F$\text{}^{2+}$ is determined to be below 50% at 2 K. A correlation between the nonradiative relaxation rate and the isotope splitting of the $\text{}^{5}$Τ$\text{}_{2}$-$\text{}^{5}$E transition is observed, demonstrating the crucial role of the dynamical Jahn-Teller coupling of the $\text{}^{5}$Τ$\text{}_{2}$ state to local Τ$\text{}_{2}$ modes for the multiphonon relaxation process. Quantum dots having a d-function density of states should exhibit no Stokes shift between absorption and emission as observed for one- and two-dimensional systems. Calorimetric absorption spectroscopy demonstrates ground state absorption coinciding in energy with the luminescence for self- organized InAs/GaAs quantum dot structures grown by MBE. Transitions into excited hole states are resolved and a comparison to photoluminescence excitation spectroscopy is presented.
    Źródło:
    Acta Physica Polonica A; 1995, 88, 4; 619-630
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Femtosecond X-ray Absorption Spectroscopy οf a Light-Driven Spin-Crossover Process
    Autorzy:
    Milne, C.
    Pham, V.
    Gawelda, W.
    Nahhas, A.
    van der Veen, R.
    Johnson, S.
    Beaud, P.
    Ingold, G.
    Borca, C.
    Grolimund, D.
    Abela, R.
    Chergui, M.
    Bressler, Ch.
    Powiązania:
    https://bibliotekanauki.pl/articles/1539083.pdf
    Data publikacji:
    2010-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Dm
    75.30.Wx
    Opis:
    Understanding the initial steps during ultrafast molecular reactions involving large spin state changes is a vital goal in structural dynamics research. These involve knowledge of the geometric structure of the system. Ultrafast X-ray absorption spectroscopy with 50-100 picosecond time resolution establishes the geometric structure of the short-lived (τ = 0.6 ns) high spin state. Here we focus on time-resolved X-ray absorption studies with 160-200 fs temporal resolution to monitor the structural evolution in this spin-conversion process.
    Źródło:
    Acta Physica Polonica A; 2010, 117, 2; 391-393
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Absorption Spectroscopy as a Probe of the Structure of Polyaminocarboxylate-Eu(III) Complexes in Solution
    Autorzy:
    Mondry, A.
    Riehl, J. P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1929802.pdf
    Data publikacji:
    1993-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.20.Wc
    78.55.Hx
    Opis:
    Absorption spectroscopy was used to study the aqueous solution structure of Eu(III) complexes with DTPA (diethylenetriaminepentaacetic acid) and TTHA (triethylenetetraaminehexaacetic acid). Analysis of the oscillator strengths of the 4f ↔ 4f transitions and of the Judd-Ofelt intensity parameters, τ$\text{}_{λ}$, was performed in order to investigate the formation and the type of bonding in Eu(III)-DTPA and Eu(III)-TTHA species occurring in solution. The correlation of these results with those from other methods made it possible to suggest a relatively complete model of Eu(III)-polyaminocarboxylate coordination.
    Źródło:
    Acta Physica Polonica A; 1993, 84, 5; 969-974
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    X-Ray Absorption Near Edge Spectroscopy of Sulfur in Biomolecules: Two Examples from Glutathione and Insulin
    Autorzy:
    Cinque, G.
    Bellisola, G.
    Colombatti, M.
    Burattini, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/2044672.pdf
    Data publikacji:
    2006-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.70.Dm
    87.64.Gb
    Opis:
    Although a minor constituent of cell and tissues, sulfur is an essential element to fulfil a wide range of biological processes, and it is present in the functional groups of many biomolecules that participate to redox reactions in vivo. Cysteine, one of the two S-containing aminoacids present in proteins, contains sulfur in fully reduced form and its thiol group can undergo a range of reactions under physiological conditions. X-ray absorption spectroscopy represents a unique tool to speciate the redox state of sulfur in biomolecules because of the known strong correlation between oxidation state and absorption edge energy shift (over 10 eV). Moreover, a rich X-ray absorption near edge structure is related to the chemical structures of S-containing biomolecules, as well as significant spectral changes due to biochemical action. The formation of a disulfide bond, i.e. a covalent linkage between the S atoms of two cysteine residues, or its reduction were investigated only indirectly in biomolecules. X-ray absorption spectroscopy experiments at the sulfur K-edge were performed at the soft X-ray beamline in Frascati using the wiggler source of the 0.51 GeV storage ring DAΦNE. X-ray absorption near edge structure data were collected to distinguish in situ between S-thiol and disulfide on model protein systems. Such preliminary results confirm this technique as a unique probe of sulfur chemistry in vivo. Quantitative speciation of S-metabolites can be foreseen in biological tissues with no chemical manipulations of the specimen.
    Źródło:
    Acta Physica Polonica A; 2006, 109, 3; 335-340
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    X-Ray Absorption Near Edge Structure and Mössbauer Spectroscopy in Study of Iron Valence States in Tissues
    Autorzy:
    Dziedzic-Kocurek, K.
    Banaś, A.
    Kwiatek, W. M.
    Stanek, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2044673.pdf
    Data publikacji:
    2006-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.18.Fs
    61.10.Ht
    Opis:
    X-ray absorption near edge structure Fe K-edge spectra and $\text{}^{57}$Fe Mössbauer spectra of selected standard compounds were recorded at room temperature. Valence and spin states of Fe in these samples known from Mössbauer spectroscopy were correlated with the shapes of X-ray absorption near edge structure spectra in search of possible application of X-ray absorption near edge structure spectroscopy as analytical tool determining local electronic states of iron in tissues. As an example, the X-ray absorption near edge structure spectra of healthy and cancerous tissues of prostate are shown, suggesting Fe$\text{}^{3+}$ in cancerous tissues.
    Źródło:
    Acta Physica Polonica A; 2006, 109, 3; 341-345
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spectroscopy and Photophysics of Monoazaphenanthrenes I. Absorption and Fluorescence Spectra of Phenanthridine and 7,8-Benzoquinoline
    Autorzy:
    Norek, M.
    Dresner, J.
    Prochorow, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2036981.pdf
    Data publikacji:
    2003-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    33.20.Lg
    33.50.Dq
    33.70.-w
    Opis:
    The absorption and fluorescence spectra of phenaentridine and 7,8-benzoquinoline have been measured in liquid solutions of non-polar, aprotic hydrocarbon solvents (n-hexane and cyclohexane) and in strongly polar (and hydrogen-bonding) methanol. The analysis of the Stokes' shift between absorption and fluorescence spectra has shown that for both molecules the observed solvent effects on their absorption and fluorescence spectra can be described in terms of universal solvent-solute interactions (no evidence of specific solvent-solute interactions, of the type of hydrogen bond formation with participation of lone-pair electrons of nitrogen atom, has been found). On the other hand, the measured decay time profiles of fluorescence are visibly longer in methanol solution than in non-polar, aprotic solvents and these observations are consistent with the observed increase in fluorescence intensity of both molecules in strongly polar methanol solution. The radiative lifetimes of the first excited singlet state do not differ noticeably for both molecules, but it has turned out that in the case of phenanthridine the nonradiative processes are getting less effective in methanol solution than in the case of 7,8-benzoquinoline, which can presumably be related to the role of different position of the substitution of nitrogen atom in these two molecules.
    Źródło:
    Acta Physica Polonica A; 2003, 104, 5; 425-439
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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