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  • 1
    ISSN: 0392-6737
    Keywords: Other interactions of matter with particles and radiation ; Infrared and Raman spectra and scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Vengono presentati e discussi risultati di EXAFS e scattering Raman in soluzioni acquose di ZnCl2 ed in soluzioni miste di ZnCl2 con LiCl, CaCl2 e SrCl2. Le misure EXAFS, effettuate mediante la facility PULS di Frascati (Italia), riguardano lo studio della struttura fine dello spettro di assorbimento sullo spigoloK dello zinco e del calcio. Le soluzioni acquose di ZnCl2 mostrano effetti di complessazione intorno allo ione zinco con un ordine locale di tipo tetraedrico. In contrasto i cationi Li+, Ca2+ e Sr2+ preferiscono una complessazione con l’acqua, con la conseguente formazione di una sfera di idratazione primaria. In eccesso di ioni cloro, le unità tetraedriche tendono a diventare sempre piú isolate e gli ioni cloro non agiscono da ponte tra le varie unità. I relativi spettri Raman confermano queste ipotesi topologiche: viene osservato, in particolare, uno spostamento a piú alte frequenze della vibrazione Raman total-simmetrica, associato alle unità tetraedriche ZnCl 4 2− , quando il rapportoR tra ioni zinco e ioni cloro è maggiore di due.
    Abstract: Резюме Приводятся данные EXAFS и данные по рамановскому рассеянию в Zn Cl2 водных растворах и в их смесях с LiCl, CaCl2 и SrCl2. Измерения, проведенные на аппаратуре PULS, на К-краяхцинка и кальция позволяют нам определить локалькый порядок около поглотителя в этих многокомпонентных системах. Водные растворы ZnCl2 обнаруживают структуру с образованием тетраэдрических комплексов около Zn2+. В противоположность этому, катионы Li+, Ca2+ и Sr2+ предпочитают комплексообразование с участием воды. В частности, получено явное подтверждение, что тетраэдрические агрегаты ZnCl 4 2− , которые представляют основные катион-анионные комплексы в таких растворах, становятся менее и менее взаимодействующими при увеличении величины отношенияR между ионами Cl− и Zn2+. Рамановский отклик подтверждает эти структурные гипотезы, указывающие, что колебательные зоны становятся более и более локализованными для величинR, больших двух.
    Notes: Summary EXAFS and Raman scattering data in ZnCl2 aqueous solutions and in their mixture with LiCl, CaCl2 and SrCl2 are presented. The measurements, carried out at the PULS facility on the Zn and CaK-edges, allow us to define the local order around the absorber in these multi-component systems. The aqueous ZnCl2 solutions exhibit inner-shell ion complexing with the formation of tetrahedral complexes about the Zn2+. In contrast, Li+, Ca2+ and Sr2+ cations prefer an inner-shell water complexation. In particular clear evidence exists that tetrahedral ZnCl 4 2− units, which are the main cation-anion complexes in such solutions, become less and less interacting for increasing values of the ratioR between Cl− and the Zn2+ ions. The Raman response confirms these structural hypotheses, indicating that the vibrational bands become more and more localized for values ofR higher than 2.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 771-781 
    ISSN: 0392-6737
    Keywords: Neutron scattering techniques (including small-angle scattering) ; Gels and sols ; Brillouin and Rayleigh scattering ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The statical and dynamical properties of lecithin/H2O/cyclohexane cylindrical reverse micelles are investigated as a function of lecithin volume fraction, ϕ, and temperature at fixed water/lecithin ratio,w 0. The viscosity data are well fitted by the Cates model when the breathing mode of micelles is taken into consideration, overlapping with the breaking and reforming mechanisms. We present some results from Brillouin-scattering experiment, performed across the sol-gel transition. In order to explain the experimentally observed ϕ-dependence of the hyperacoustic parameters, a mechanical model was developed from which the ϕ-dependence of the micelle size distribution was obtained. From a comparison with the viscosity data the entanglement length was estimated. Furthermore some new results from an incoherent quasi-elastic neutron scattering experiment are presented. The whole body of the experimental results suggests for a sol-gel transition triggered by topologic phenomena. When the lecithin volume fraction increases, the kinetic equilibrium between the breaking and reforming mechanisms of the micelles shifts the mean micelle length towards higher values and the entanglement of the micelles becomes highly favourable. The obtained results are discussed and compared with other findings in literature.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 9 (1987), S. 829-844 
    ISSN: 0392-6737
    Keywords: Other interactions of matter with particles and radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Nel presente lavoro si presentano e si discutono i risultati di misure EXAFS, di Rayleigh wing e di scattering Raman nella miscela SbCl3/H2O. Le misure EXAFS, eseguite presso i laboratori PULS di Frascati, sia sullo spigoloK del cloro che sugli spigoliL I, II, III dell’antimonio, permettono di ottenere informazioni sull’ordine locale del sistema. In particolare si evidenziano formazioni di legami intramolecolari Sb−Cl ed intermolecolari Sb...Cl che sono simili nelle distanze e nella coordinazione a quelli esistenti nel fuso. Si definisce anche il ruolo dell’acqua che, coordinandosi con i clori, agisce da ponte tra catene di tricloruro di antimonio. Le misure di scattering di luce confermano le ipotesi strutturali emerse dai risultati di spettroscopia EXAFS: la simmetria originaleC 3v della molecola SbCl3 si abbassa nell’interazione con l’acqua. Inoltre nuove bande vibrazionali appaiono negli spettri Raman, legati all’interazione cloro-acqua. Infine nella regione spettrale a bassa frequenza si evidenziano modi cooperativi connessi con la presenza di una densità di stati vibrazionali.
    Abstract: Резюме В работе приводятся данные для рзлеевского крыла EXAFS и комбинационного рассеяния в смеси SbCl3/H2O. Измерения наK-кра Cl иL I, II, III-краях, как функция температуры, позволяют нам определить локальный порядок около поглотителя. В частности, отмечается, что внутримолекулярные Sb−Cl и межмолекулярные Sb...Cl расстояния и координация оказываются сходными с величинами, существующими в чистом SbCl3. Анализ данных также показывает, что молекулы воды связаны с хлором, что приводит к кросс-связи межлу цепочками SbCl3. Рассеяние света подтверждает эти структурые гипотезы, указывая на то, что примитивнаяC 3v симметрия молекулы SbCl3 уменьшается из-за присутствия воды. Также подтверждается, что образуются новые колебательные зоны благодаря связям хлора с водой. В заключение, мы детектируем фононно-подобный вклад в низкочастотной области, который дает эффективную плотность рамановских колебательных состояний.
    Notes: Summary EXAFS Rayleigh wing and Raman-scattering data in SbCl3/H2O mixture are presented. The measurements, carried out at the PULS facility on the ClK-edge and on theL I, II, III-edges as a function of temperature, allow us to define the local order around the absorber. In particular, clear evidence exists that intramolecular Sb−Cl and intermolecular Sb...Cl distances and coordination, similar to the ones existing in pure SbCl3, are present. The data analysis reveals also that the water molecules are linked to the chlorine, giving rise to a cross-link between the antimony trichloride chains. The light scattering response confirms these structural hypotheses, indicating that the primitiveC 3v symmetry of the SbCl3 molecule is lowered by the water presence. Evidence also exists that new vibrational bands are originated by the chlorine-water bonds. Finally we detected a phononlike contribution, in the low-frequency region, that gives an effective Raman vibrational density of states.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 12 (1990), S. 657-671 
    ISSN: 0392-6737
    Keywords: Kinetic and transport theory ; Classical, semiclassical, quantum theories of liquid structure ; Studies of specific liquid structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Vengono presentati risultati di EXAFS e scattering Raman in soluzioni acquose di sali II-I (ZnCl2 e sue miscele con LiCl eCaCl2) e III-I (SbCl3+H2O). Viene mostrato che lo ZnCl2 presenta una coordinazione tetraedrale intorno allo Zn2+ mentre Li+ e Ca+ preferiscono coordinarsi solo con l'acqua. Si mostra inoltre che le unità tetraedrali diventano sempre meno interagenti man mano che il rapporto Cl−/Zn2+ cresce. Questo risultato strutturale è confermato dallo scattering Raman ove le bande vibrazionali diventano sempre più localizzate per valori di Cl−/Zn2+ maggiori di 2. Per quanto riguarda la miscela SbCl3+H2O EXAFS mostra una coordinazione Sb−Cl e Sb...Cl molto vicina a quella del puro SbCl3. Le molecole di acqua si legano ai clori dando luogo a un cross-link tra le catene di SbCl3. Il Raman conferma questo risultato mostrando che la simmetriaC 3v della molecola SbCl3 si abbassa in presenza dell'acqua.
    Abstract: Резюме Предлагаются данные по Рамановскому рассеянию и EXAFS на воднях растворах солей II-I и III-I. В качестве соли II-I, исследована система ZnCl2 и её смесь с LiCl и CaCl2. Показывается что ZnCl2 обнаруживает тетраэдрическую структуру около иона Zn2+, тогда как ионы Li+ и Ca+ предпочитают комплексообразование с внутренней оболочкой воды. В частности, показывается, что тетраэдрические структуры становятся менее и менее взаимодействующими, когда отношение Cl−/Zn2+ увеличивается. Такие структурные результатя подтверждаются данными по Рамановскому рассеянию, что указывает на то, что колебательные зоны становятся более и более локализованными для значений Cl/Zn2+, больших чем 2. Что касается солей III-I, мы приводим данные для смеси SbCl3/H2O. Данные по EXFAS указывают, что связи Sb−Cl и Sb...Cl очень близки к связям чистого SbCl3. Молекула воды, по-видимому, связана с хлором, что приводит к поперечной связи между SbCl3-цепочками. Рамановское рассеяние подтверждает эти результаты, указывая на то, чтоC 3v симметрия молекулы SbCl3 уменьшается в присутствии воды.
    Notes: Summary We present results from EXAFS and Raman scattering on aqueous solutions on II-I and III-I salts. As II-I salt the system investigated was the ZnCl2 and its mixture with LiCl, CaCl2 and SrCl2. It was shown that ZnCl2 evidences a tetrahedral arrangement around the Zn2+ ion whereas Li+, Ca+ and Sr2+ ions prefer an inner-shell water complexation. In particular it was shown that the tetrahedral units become less and less interacting when the ratio Cl−/Zn2+ is increasing. Such structural results are confirmed by the Raman probe that shows the vibrational bands becoming more and more localized for Cl−/Zn2+ values higher than 2. For what III-I salts are concerned we report results on SbCl3/H2O mixture. EXAFS evidenciates an Sb−Cl and Sb...Cl coordination very close to that of pure SbCl3. The water molecule appears linked to the chlorine giving rise to a cross-link between SbCl3 chains. Raman confirms such a result showing that the C3v symmetry of SbCl3 molecule is lowered in the presence of water and shows a new chlorine-water contribution plus a phononlike contribution in the very lowfrequency region.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 103-117 
    ISSN: 0392-6737
    Keywords: Infra-red and Raman spectra and scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Nel presente lavoro si discutono i risultati di misure EXAFS e Raman in miscele di elettroliti forti (ZnBr2, CuBr2, SrBr2) in H2O. Le misure EXAFS, eseguite presso i laboratori PULS di Frascati, e le misure di spettroscopia Raman, eseguite presso i nostri laboratori di scattering di luce, ci hanno permesso di studiare sia la statica che la dinamica di questi sistemi. In particolare, si evidenziano le formazioni di coppie ioniche metallo-alogeno e di sfere d’idratazione. I risultati sono discussi in termini dei già esistenti modelli strutturali.
    Abstract: Резюме В этой работе обсуждаются спектры EXAFS и рамановские спектры, полученные в смесях сильных электролитов (ZnBr2, CuBr2, SrBr2) в воде. Измерения проводились на ADONE в фраскати для измерения EXAFS и в лаборатории рассеяния света для измерения рамановского рассеяния. Результаты измерений дают информцию о статических и динамических свойствах этих систем. В частности, обнаружено образование ионных пар металл-галоген и областей гидратции. Полученные результаты обсуждаются в рамках существующщих структурных моделей.
    Notes: Summary EXAFS and Raman spectra, obtained from mixed MBr2+NBr2 (M, N=Zn2+, Cu2+, Sr2+) in H2O are discussed. The measurements, carried out at Adone (PULS facility), for EXAFS and in our light scattering laboratory, for Raman, allow us to study both the static and the dynamic properties of these systems. In particular, strong evidence of metal-halogen ionic pairs and hydration shell formation is reported. Our results, in terms of existing structural models, are also discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physica B: Physics of Condensed Matter 180-181 (1992), S. 861-864 
    ISSN: 0921-4526
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 6541-6545 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 733-736 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2243-2245 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: All parameters of a spectrometer, signal detection, and normalization of the recorded Raman signal were controlled by a compatible IBM PC/XT computer which was connected to a Spex Ramalog 5 system. By the use of a motor-driven polarizer, we are able for each single step time of the instrument, to monitor simultaneously the contributions IVV and IVH of the spectrum. Moreover, the simultaneous normalization of the signal with the intensity of the exciting laser light allows one to avoid the effects of the unwanted laser instability. The program can be requested by electronic mail.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 942-947 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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