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Wyświetlanie 1-7 z 7
Tytuł:
Positron Annihilation with Core Electrons in 3d-Transition Metals
Autorzy:
Baranowski, A.
Dębowska, E.
Powiązania:
https://bibliotekanauki.pl/articles/1933461.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.Bj
71.90.+q
Opis:
Recently we have been able to resolve the rare gas core contribution in long-slit angular correlation of annihilation radiation curves for some d-metals when applying a new model to fit the experimental data. In the present paper the model is applied to angular correlation of annihilation radiation spectra for the whole series of the 3d-transition metals from Sc to Cu. The model corresponds to recent theoretical predictions for the metals from the second half of the series and allows one to find the contribution of the core electrons to the whole annihilation process for these metals. Probably a different description of the angular correlation of annihilation radiation data for the metals from the beginning of the 3d-series should be searched.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 13-19
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultramarine, Lazurite and Sodalite Studied by Positron Annihilation and EPR Methods
Autorzy:
Baranowski, A.
Dębowska, M.
Jerie, K.
Jezierski, A.
Sachanbiński, M.
Powiązania:
https://bibliotekanauki.pl/articles/1933463.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.-g
61.90.+d
76.30.-v
Opis:
Studies of positron annihilation accompanied by EPR technique were undertaken for sodalite and lazurite and their synthetic counterparts (synthetic sodalite and ultramarines). Results of measurements performed by two techniques of positron annihilation spectroscopy (angular correlation of annihilation radiation, ACAR, and positron annihilation lifetime) revealed the undoubted influence of free radicals on positron annihilation mechanism but both inhibition of positronium formation by them and the effect of filling cages ought to be taken into account. The distinct differences between ACAR curves for sodalites, lazurites and ultramarines probably reflect the presence of different radicals in their cages and chemical heterogeneity as well as the disorder in Al, Si-site ordering in case of ultramarines. Comparison of the results of ACAR measurements with the ones of the EPR studies indicates that there is correspondence between them. Similarly to three families of the ACAR curves, different likes of EPR lines were obtained for three groups of samples; sodalites, lazurites and ultramarines. It is possible that the annihilation of positrons takes place mainly with unpaired electrons recorded by the EPR technique.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 29-41
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Carbon Black--polyethylene Composites Studied by Positron Annihilation
Autorzy:
Dębowska, M.
Rudzińska-Girulska, J.
Pasternak, A.
Poźniak, R.
Powiązania:
https://bibliotekanauki.pl/articles/2007961.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.Bj
82.30.Hk
Opis:
Preliminary results of positron annihilation lifetime measurements, performed for carbon black-LDPE composites with three kinds of carbon black (PRINTEX XE2, VULCAN XC-72, and SAKAP 6) are presented. Four components with lifetimes τ$\text{}_{1}$≈ 120 ps, τ$\text{}_{2}$≈340 ps, τ$\text{}_{3}$≈1.2 ns, τ$\text{}_{4}$≈2.8 ns occurred to be the best fitted to measured positron lifetime spectra. The presence of carbon black resulted only in reduction of intensities of the components with the lifetimes τ$\text{}_{1}$, τ$\text{}_{3}$, τ$\text{}_{4}$ (originating in our opinion from the annihilation of the positronium) and increase in the intensity of the component with the lifetime τ$\text{}_{2}$. The intensities depend both on the content of carbon black and its kind as well. The strongest influence of the carbon black of the highest specific surface area (PRINTEX XE2) has been observed at the intensities which correlate well with the results of studies of resistivity and tensile strength for the same samples.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 509-514
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Free Volume in Epoxy-Coal Resins Studied by Positron Annihilation
Autorzy:
Baranowski, A.
Dębowska, M.
Jerie, K.
Kurzeja, L.
Hennek, K.
Rudzińska-Girulska, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933465.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
81.20.Sh
78.70.Bj
82.30.Hk
Opis:
In this paper the macroscopic properties of the tetrafunctional epoxy resin (N, N'-tetraglycidyl ether of diaminodiphenylmethane) cured by 4, 4'-diaminodiphenylmethane, were studied. For the system the influence of various curing conditions on the glass temperature was investigated. Results obtained for two compositions: an unmodified one and a modified with coal were compared with information on the free volume given by the positron annihilation technique.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 43-49
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Liquid Crystalline Polyurethanes Studied by Positron Annihilation Method
Autorzy:
Baranowski, A.
Dębowska, M.
Jankowski, A.
Jerie, K.
Penczek, P.
Rudzińska-Girulska, J.
Szczepaniak, B.
Wolińska-Grabczyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/1933462.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
81.20.Sh
78.70.Bj
82.30.Hk
Opis:
A series of liquid crystalline polyurethanes of different both flexible spacer length and mesogenic group content was studied by means of positron annihilation method. The investigated polymers were targeted on the separation of aromatic hydrocarbons from their mixtures with aliphatic ones. The effect of modification of the liquid crystalline polyurethane chain on the polyurethane free volume size and free volume distribution was determined on the basis of the positron annihilation lifetime spectra. In the positron annihilation lifetime spectra measured for the samples under study two long components of several nanoseconds, characteristic of o-Ps decaying by pick-off, occurred. The correlation of the values of the o-Ps lifetime with the size of the free volume region allowed to recover the free volume distributions with the use of the method employing the numerical Laplace inversion technique. The obtained results were compared with the diffusion data on the mobility of liquid hydrocarbons in the liquid crystalline polyurethanes enabling the correlations between polymer structure and its transport properties to be evaluated.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 21-27
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation Studies of Styrene-N-X-Phenylmaleimides
Autorzy:
Baranowski, A.
Dębowska, M.
Jerie, K.
Rudzińska-Girulska, J.
Pawełka, Z.
Sikorski, R. T.
Powiązania:
https://bibliotekanauki.pl/articles/1933467.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.Βj
81.20.Sh
82.30.Hk
Opis:
Results of angular correlation of annihilation radiation and positron annihilation lifetime measurements are presented for five styrene copolymers: poly(co-styrene-phenylmaleimide) and its three derivatives with chlorine as well as for one with the OH group substituted in the benzene ring. It occurs that the chlorine substituted in three different positions in the benzene ring poly(co-styrene-o (or -m, -p)-chlorophenylmaleimide) inhibits the formation of the positronium to different extent. The greatest effect is observed in case of the chlorine atoms substituted in the benzene ring at ortho-position towards the nitrogen atom. In addition, electric dipole moments were measured for N-X-phenylmaleimide units, to check whether their magnitude influences the positron annihilation parameters. On the basis of the present results no correlation between the positron annihilation parameters and the electric dipole moments of the units was noticed.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 51-57
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Chloropolystyrenes
Autorzy:
Baranowski, A.
Dębowska, M.
Jerie, K.
Mirkiewicz, G.
Rudzińska-Girulska, J.
Sikorski, R. T.
Powiązania:
https://bibliotekanauki.pl/articles/1928863.pdf
Data publikacji:
1993-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.60.+z
78.70.Bj
81.20.Sh
82.30.Hk
Opis:
Results of angular correlation of annihilation radiation and positron annihilation lifetime measurements are presented for atactic polystyrene and chloropolystyrenes. The inhibition of positronium formation follows the chlorine introduction as the decrease in intensities of the narrow component in angular correlation of annihilation radiation curves and of the longest-lived component in positron annihilation lifetime spectra prove. In general, the chlorine "activity" towards positrons seems to depend on its position in the polymer structure. The annihilation rate distribution as well as the radius and volume distributions of free-volume sites where positronium is assumed to be formed obtained with the use of CONTIN program for the raw sample in the 2nd series are given additionally.
Źródło:
Acta Physica Polonica A; 1993, 83, 3; 239-249
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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