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Wyświetlanie 1-15 z 58
Tytuł:
Prospects of Positronium Spin Rotation Using for Medium Investigation
Autorzy:
Baryshevsky, V. G.
Metelitsa, O. N.
Powiązania:
https://bibliotekanauki.pl/articles/1933470.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
Opis:
The feasible applications of a new positron spectroscopy technique based on measuring of the time oscillation under positronium annihilation is analyzed.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 67-72
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
To the Possibility of Measurements of Orthopositronium Annihilation Amplitudes for QED Testing
Autorzy:
Baryshevsky, V. G.
Metelitsa, O. N.
Powiązania:
https://bibliotekanauki.pl/articles/1933471.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
Opis:
In connection with previously revealed disagreement of theoretically calculated and measured orthopositronium decay rate in vacuum we suggest the experiment to clarify which of the positronium annihilation amplitudes R$\text{}_{m}$,m = 0,±1 causes this disagreement. The developed for this purpose experimental procedure can also be used as the basis for the new area of positron spectroscopy, connected with the investigation of the anisotropic (spin dependent) interaction of positronium in the media.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 73-78
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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:
Some Comments on p-Ps and Density Parameter
Autorzy:
Goworek, T.
Wawryszczuk, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933488.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
Opis:
The constraint-free analysis of several representative positron lifetime spectra was performed with the resolution time of 144 ps. The role of p-Ps parameters in understanding of the positronium structure in solids is discussed.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 135-138
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pressure Effects in ortho-Positronium Annihilation
Autorzy:
Goworek, T.
Wawryszczuk, J.
Zaleski, R.
Powiązania:
https://bibliotekanauki.pl/articles/2042179.pdf
Data publikacji:
2005-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
Opis:
A short review of experiments concerning the influence of high pressure on positron annihilation in molecular solids is given. To this kind of experiments belong e.g. pressure inhibition of positronium formation, pressure induced phase transitions, and free volume swelling in the media intercalated by high pressure gas.
Źródło:
Acta Physica Polonica A; 2005, 107, 4; 608-614
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Formation in Solid Long-Chain Alkanes
Autorzy:
Zaleski, R.
Wawryszczuk, J.
Goworek, T.
Powiązania:
https://bibliotekanauki.pl/articles/2042188.pdf
Data publikacji:
2005-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
Opis:
This paper represents a fragment of systematic studies on positron annihilation in solid saturated hydrocarbons (alkanes, paraffins) from C$\text{}_{17}$H$\text{}_{36}$ to C$\text{}_{30}$H$\text{}_{62}$. The Tao-Eldrup model and its extensions allow to identify the places in the crystalline structure where positronium is trapped, and estimate respective trap sizes. In the rigid phase I positronium locates mainly in two-dimensional empty spaces between the lamellae of crystal structure. Additional free volumes exist in high temperature phases due to appearance of n-alkane conformers representing a non-planar molecule distortion. The rise of ortho-positronium intensity with the sample irradiation dose, which was seen earlier in polymers, is observed also in n-alkanes. One can find similarities between the ortho-positronium annihilation in crystalline alkanes and polymers, like exponential character of that rise, and the trap bleaching by illumination. It confirms the same origin of the intensity growth, i.e. the accumulation of trapped electrons. Two kinds of electron traps were found. The time constant of electron accumulation in the traps depends on the carbon chain length and varies with temperature in different way for even- and odd-numbered alkanes.
Źródło:
Acta Physica Polonica A; 2005, 107, 4; 635-641
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Three-Quantum Annihilation in Porous Vycor Glass
Autorzy:
Jasińska, B.
Wawryszczuk, J.
Zaleski, R.
Powiązania:
https://bibliotekanauki.pl/articles/2043332.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
Opis:
Three methods of determination of 3γ o-Ps decay intensity are compared. The estimate of 3γ fraction obtained from classical lifetime measurements can be distorted due to a higher absorption of theγ quanta from the continuous spectrum of three-quantum decay, compared to two-quantum one.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 821-825
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oscillations in Orthopositronium Annihilation in Magnetic Field in SiO$\text{}_{2}$ Powders
Autorzy:
Berestov, A. V.
Talat, A. S.
Baranov, V. V.
Rudak, E. A.
Martsynkevich, B. A.
Powiązania:
https://bibliotekanauki.pl/articles/1933473.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
07.85.+n
36.10.Dr
78.70.Bj
Opis:
The observation method of γ-quantum angular distribution oscillations in positronium annihilation in magnetic field is essentially improved. Oscillation parameters in the experiment are in agreement with theoretical estimations.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 79-82
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Discrete and Continuous Analysis of Positron Lifetime Spectra: a Comparison
Autorzy:
Consolati, G.
Quasso, F.
Powiązania:
https://bibliotekanauki.pl/articles/2007998.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
71.60.+z
78.70.Bj
Opis:
Positron lifetime spectra in poly[1-(trimethylsilyl)]propine membranes were collected at different temperatures and various number of accumulated counts, in order to compare the results from analyses obtained by different decay models: discrete (that is, purely exponential) or continuous (with at least one distribution of lifetimes). Analysis into four discrete components is inadequate, unless a low number of counts (1 to 2 millions) is accumulated. Conversely, deconvolutions which allow the ortho-positronium lifetime to be distributed give satisfactory fits, even at the highest statistics (60 millions). An equivalent good fit in terms of χ$\text{}^{2}$ test is obtained with a five discrete components analysis, from which it is possible to extract information on the first moments (centroid and standard deviation) of ortho -positronium lifetime distribution.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 505-508
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Formation in Organic Liquids
Autorzy:
Karbowski, A.
Fedus, K.
Służewski, K.
Bruzdowska, J.
Karwasz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1030028.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
82.30.Gg
36.10.Dr
Opis:
This paper reports on the results of positron annihilation lifetime measurements of three organic liquids: benzene (C₆H₆), cyclohexane (C₆H₁₂), and methanol (CH₃OH). The lifetime spectra are acquired at different temperatures for non-degassed, degassed, and oxygen-saturated samples, at temperatures between 5°C and 25°C. The spectra are analyzed using a standard three-exponential model. The influence of oxygen on each lifetime and intensity component is discussed.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1466-1469
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Formation in Nanostructured Metals
Autorzy:
Čížek, J.
Melikhova, O.
Hruška, P.
Vlček, M.
Anwand, W.
Liedke, M.
Novotný, M.
Bulíř, J.
Powiązania:
https://bibliotekanauki.pl/articles/1033937.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
41.75.Fr
36.10.Dr
Opis:
Positronium formation in Au films was studied using a magnetically guided continuous slow positron beam with variable energy. Black Au film with porous morphology was compared with conventional smooth Au film. In the smooth Au film positronium is formed on the film surface only. The black Au film exhibits porous sub-surface region containing micro-cavities interconnected with surface. Positronium is formed on inner surfaces of micro-cavities in the sub-surface region and travels through interconnected cavities towards the surface. 3-γ annihilation of ortho-positronium leaves a clear signature in two-dimensional coincidence Doppler broadening spectra. Measures of 3-γ annihilation contribution calculated from single γ-ray and coincidence Doppler broadening spectra were calculated and compared.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1579-1584
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Formation at Low Temperatures in Polymers and Other Molecular Solids
Autorzy:
Hirade, T.
Powiązania:
https://bibliotekanauki.pl/articles/2042181.pdf
Data publikacji:
2005-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
36.20.Kr
Opis:
Positronium (Ps) formation by weakly localized long-lived electrons (trapped electrons or anions) and positrons at low temperatures successfully explained the Ps formation enhancement at low temperatures observed in polymers and molecular solids. This Ps formation process is different from Ore process and spur process. The phenomena expected by this Ps formation mechanism, such as an effect due to visible light exposure, a density dependence of weakly localized electrons and the delayed Ps formation were successfully observed as the experimental evidence of this Ps formation process. Some possibilities for application of this new Ps formation were also given. One is a new idea for estimation of spin polarity of positrons. Another is the possibility of application to study the local molecular motion by observing the decay of Ps formation intensity.
Źródło:
Acta Physica Polonica A; 2005, 107, 4; 615-622
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Revision of the Model of Formation of Radiolytic Products in Aqueous Solutions
Autorzy:
Stepanov, S. V.
Byakov, V. M.
Powiązania:
https://bibliotekanauki.pl/articles/2042192.pdf
Data publikacji:
2005-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.80.Fe
36.10.Dr
78.70.Bj
Opis:
Mathematical model of formation of radiolytic products (e$\text{}_{aq}^{-}$, H, OH, H$\text{}_{2}$, H$\text{}_{3}$O$\text{}^{+}$, OH$\text{}^{-}$, Ps) in water is developed. It takes into account (1) reactions between dissolved scavengers of thermalized and hydrated electrons as well as epithermal ones; (2) ambipolar diffusion expansion of the intratrack species; (3) additional channels of Ps and H$\text{}_{2}$ formation due to appearance of weakly trapped electrons. Good agreement is obtained with experimental data on kinetics of accumulation of the products in pure water and their concentration variations in aqueous solutions.
Źródło:
Acta Physica Polonica A; 2005, 107, 4; 651-660
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of Coincidence Doppler Broadening Spectroscopy to Hydrocarbons at Different Substance States
Autorzy:
Yu, R.
Suzuki, T.
Ito, Y.
Djourelov, N.
Kondo, K.
Shantarovich, V. P.
Powiązania:
https://bibliotekanauki.pl/articles/2042205.pdf
Data publikacji:
2005-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
82.30.Gg
78.70.Bj
Opis:
Coincidence Doppler broadening spectroscopy was applied to study n-hexane (C$\text{}_{6}$H$\text{}_{14}$), cyclohexane (C$\text{}_{6}$H$\text{}_{12}$) and cyclohexanone (C$\text{}_{6}$H$\text{}_{10}$O), at solid, as well as liquid states. The experiments were performed in parallel with traditional positron annihilation lifetime spectroscopy. Significant positron trapping by oxygen was observed in cyclohexanone; the oxygen effect is stronger in liquid state than in solid one, which can possibly be attributed to positron solvation in polar solution. Coincidence Doppler broadening results for n-hexane and cyclohexane indicate an existence of higher energetic annihilation electrons in Ps-bubble forming liquids than that in solids.
Źródło:
Acta Physica Polonica A; 2005, 107, 4; 697-701
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Study of Positronic Atoms with Adiabatic Separation of Positronic Motion
Autorzy:
Strasburger, K.
Wołcyrz, M.
Powiązania:
https://bibliotekanauki.pl/articles/1812552.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
34.20.Cf
31.50.Bc
36.10.Dr
Opis:
A modified adiabatic approximation, with the positron treated as a light nucleus and its charge included only partially in the electronic Hamiltonian, was applied to compute the energies and properties of bound states of lithium positride, positronic beryllium and positronic magnesium. The electronic Schrödinger equation was solved with the configuration interaction method. No bound state was obtained for lithium positride, while the dissociation energies of positronic beryllium and positronic magnesium were underestimated by 2.6 and 7 millihartrees, respectively. Consequences for the applicability of the adiabatic approximation to describe positronic systems are discussed.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1533-1542
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 58

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