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Wyszukujesz frazę "Duplâtre, G." wg kryterium: Autor


Wyświetlanie 1-7 z 7
Tytuł:
Current Problems and Unknowns in Positronium Dynamics
Autorzy:
Duplâtre, G.
Powiązania:
https://bibliotekanauki.pl/articles/1812489.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
Opis:
A survey is made on positronium dynamics in liquids. From literature data, it is shown that applying conventional kinetics to positronium reactions leads to quite satisfactory results in a large variety of solvents, solutes, reaction types and temperatures. On the opposite, applying the theoretically well established concepts of positronium bubble state and time-dependent reaction rate coefficient would imply the use of unrealistic solute radii in the related kinetic equations, with possible exception of large solutes (micelles). Some solutes displaying unexpectedly high reaction rate constants are shown to be refractory to any of the above quantitative approaches. The particular case of reversible positronium bound-state formation is further examined, the most consistent results arising, again, from the conventional analysis of the data.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1347-1358
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positrons and Positronium Atoms in a Condensed Phase Close to Its Melting Point
Autorzy:
Stepanov, S.
Zvezhinskiy, D.
Byakov, V.
Duplâtre, G.
Stepanov, P.
Powiązania:
https://bibliotekanauki.pl/articles/1196038.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
34.80.Lx
78.70.Bj
82.30.Gg
Opis:
Investigation of the local heating effect at the terminal part of a fast positron track sheds light on the accumulation of defects in a frozen medium close to its melting point. Estimations of the formation energies of the structural defects which may trap the Ps atom as well as a contribution of these defects to the enthalpy of fusion are obtained.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 691-695
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Track Effects in Positronium Formation
Autorzy:
Stepanov, S.
Byakov, V.
Duplâtre, G.
Stepanov, P.
Bokov, A.
Powiązania:
https://bibliotekanauki.pl/articles/1030026.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
positron
positronium
annihilation
ion-electron recombination
solvation
mobility
external electric field
track effects
polar and nonpolar liquids
Opis:
We discuss some aspects important for interpretation of the Ps formation process in liquids and molecular media: (1) inhomogeneity of intratrack reactions and parameters of the e⁺ track, (2) final states of e⁺, its solvation in polar and nonpolar liquids, relation to e⁺ mobility, (3) quasi-neutrality of the e⁺ blob and its ambipolar outdiffusion, (4) appearance of the "in-blob" and "out-of-the-blob" positron fractions, and (5) electric field effect on Ps formation.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1461-1465
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Formation of Quasi-Free and Bubble Positronium States in Water and Aqueous Solutions
Autorzy:
Stepanov, S.
Duplâtre, G.
Byakov, V.
Zvezhinskiy, D.
Subrahmanyam, V.
Powiązania:
https://bibliotekanauki.pl/articles/1338623.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
34.80.Lx
82.30.Gg
Opis:
It is shown that in aqueous solutions a positronium atom is first formed in the quasi-free state, and, after 50-100 ps, becomes localized in a nanobubble. Analysis of the annihilation spectra of $NaNO_3$ aqueous solutions shows that the hydrated electron is not involved in the positronium (Ps) formation.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 770-774
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Kinetics of the Spin-Conversion of Positronium Measured by β$\text{}^{+}$γ∆E Age-Momentum Correlation
Autorzy:
Lauff, U.
Maier, K.
Major, J.
Seeger, A.
Stoll, H.
Wesołowski, P.
Koch, M.
Bilard, I.
Abbé, J.
Duplâtre, G.
Powiązania:
https://bibliotekanauki.pl/articles/1929104.pdf
Data publikacji:
1993-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
Age-momentum correlation (AMOC) measurements provide time-resolved information on the momentum distribution of annihilating electron-positron pairs through correlated determination of Doppler broadening (∆E) of the 511 keV annihilation radiation line and positron age. In the β$\text{}^{+}$γ∆E AMOC technique implemented at the Stuttgart pelletron accelerator the start signals for the age measurements are generated when the relativistic positrons pass through a fast plastic scintillator, which has a detection efficiency close to unity. Beam-based β$\text{}^{+}$γ∆E AMOC measurements thus combine high β$\text{}^{+}$γ∆E triple-coincidence rates with low background. From a practical point of view this constitutes a major progress compared to conventional (source-based) γγ∆E AMOC measurements. The AMOC technique permits direct access to a wide variety of time-dependent processes, among them the reaction kinetics in positronium chemistry. As an example, we present a β$\text{}^{+}$γ∆E AMOC investigation of the kinetics of a spin-conversion reaction of positronium in methanol induced by the presence of a nitrosyl free-radical paramagnetic solute (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl , HTEMPO). The AMOC measurements allowed the time-resolved observation of the spin-conversion process, which had been investigated before by uncorrelated positron lifetime and Doppler-broadening measurements. It is found that within the concentration range investigated (≤ 0.1 mol/l) the spin-conversion reaction rate at room temperature depends linearly on the HTEMPO concentration with a reaction-rate constant k$\text{}_{conv}$ = (22.5 ± 0.5) × 10$\text{}^{9}$ l mol$\text{}^{-1}$ s$\text{}^{-1}$.
Źródło:
Acta Physica Polonica A; 1993, 83, 3; 349-358
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positrons and Positroniu m in Grainy and Porous Solids
Autorzy:
Kajcsos, Zs.
Liszkay, L.
Duplâtre, G.
Varga, L.
Lázár, K.
Pál-Borbély, G.
Beyer, H.
Lohonyai, L.
Caullet, P.
Patarin, J.
Powiązania:
https://bibliotekanauki.pl/articles/2025110.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
36.10.Dr
61.43.Gt
Opis:
Systematic investigations have been performed using positron annihilation techniques on micrograins of crystalline powders (e.g., MgO, Al$\text{}_{2}$O$\text{}_{3}$, SiO$\text{}_{2}$) and on various zeolites (e.g., silicalite 1, Na-X, Na-Y, ZSM-5, mordenite) aiming at a better under standing of the formation and decay of the long-lived ortho-positronium states. The techniques were lifetime spectroscopy, Doppler-effect measurements and the recording of the full energy distribution of the annihilation radiation. The influences of heat treatment, sample evacuation and presence of gases were investigated. Lifetimes over 130 ns and o-Ps fractions of about 30% were found. A strong correlation of positron annihilation technique data with a water content of the samples was evidenced. Possible pictures of the formation and decay of ortho-positronium in porous media are discussed.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 399-406
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Trapping in Porous Solids: Means and Limitations for Structural Studies
Autorzy:
Kajcsos, Zs.
Liszkay, L.
Duplâtre, G.
Varga, L.
Lohonyai, L.
Pászti, F.
Szilágyi, E.
Lázár, K.
Kótai, E.
Pál-Borbély, G.
Beyer, H. K.
Caullet, P.
Patarin, J.
Azenha, M. E.
Gordo, P. M.
Lopes Gil, C.
de Lima, A. P.
Ferreira Marques, M.
Powiązania:
https://bibliotekanauki.pl/articles/2042216.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
61.43.Gt
Opis:
Positron annihilation techniques are used for the structural investigation of solids but the interpretation of results in grainy and porous media is still unclear. A unique picture can be obtained assuming that the dominant process is Ps trapping in competing "extended free volume" sites. In samples with a large amount of free volumes near-saturation Ps trapping will rule the lifetime pattern, and very long lifetimes of over 100 ns might arise from o-Ps trapped in mesopores. It is shown that lifetime parameters must be corrected for the 3γ/2γ counting efficiency ratio. The results demonstrate the high sensitivity of Ps to mesopores in zeolites but also that Ps-trapping poses limitations on the applicability of lifetime to structural investigation in porous systems. The evolution of the lifetime spectra upon changes in the sample and measuring conditions should be considered in a complex way, observing not only changes in some selected components but in the whole lifetime pattern simultaneously.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 729-737
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-7 z 7

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