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1
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Relativistic Phenomena in Two-Quantum Annihilation of Electron-Positron Pairs

100%
Baranowski A.
Acta Physica Polonica A
|
2006
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vol. 110
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issue 5
551-558
EN
The kinematics of e^+e^- pair and annihilation quanta momentum vectors have been presented basing on ellipse and spheroid properties. Using the formulae resulting from the Lorentz transformation of momentum and energy there was pointed out that the aberration and the longitudinal and transversal Doppler effects are inseparably associated.
2
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Positron Annihilation with Core Electrons in 3d-Transition Metals

64%
Baranowski A., Dębowska E.
Acta Physica Polonica A
|
1995
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vol. 88
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issue 1
13-19
EN
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.
3
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Positron Annihilation in and Compressibility of Water-Organic Mixtures. The System Water-Acetamide

52%
Jerie K., Baranowski A., Gliński J., Orzechowski K.
Acta Physica Polonica A
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1996
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vol. 90
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issue 6
1169-1177
EN
The experimental results of positron annihilation experiments in aqueous solutions of acetamide were compared to those of ultrasonic velocity. The system under investigation behaves untypically when changing acetamide concentration. From the point of view of surface tension it interacts with water like normal alcohols, while the positron annihilation and ultrasonic results suggest hydrophilic hydration and lack of hydrophobic interactions.
4
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Positron Trapping Rate Coefficient for Thermalized Positrons at Metal-Dielectric Interface

52%
Baranowski A., Ewertowski R., Świątkowski W.
Acta Physica Polonica A
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1991
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vol. 79
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issue 4
517-523
EN
On the basis of experimental positron lifetime spectra it was shown that positrons can be trapped at metal-dielectric interface. The coefficient indicating the trapping possibility of the AgŃa_{3}AlF_{6} interface has been evaluated.
5
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Test Measurements of Modernized Version of Two-Detector Doppler Spectrometer

52%
Baranowski A., Kostrzewa M., Szuszkiewicz M.
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vol. 95
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issue 4
439-447
EN
Basing on the electronic analogue modules in adding and subtracting branches of pulses, a modernized two-detector Doppler spectrometer has been constructed using only one multichannel analyser. Doppler spectra for Al, Ni, Ag have been measured. ACARFIT computer program was used to compare the Doppler and angular correlation of annihilation radiation results.
6
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Structure of Carbon Tetrachloride + t-Butanol Mixtures from Positron Annihilation and Ultrasonic Velocity Measurements

52%
Jerie K., Baranowski A., Gliński J.
Acta Physica Polonica A
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1993
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vol. 83
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issue 3
313-320
EN
The densities of and sound velocities in t-butyl alcohol solutions in CCl_{4} were determined in temperature range 25 to 45°C. From these data the adiabatic compressibility coefficients of the solutions were calculated, as well as excess densities and compressibilities. The positron annihilation spectrum for this system in room temperature was measured. The results plotted against alcohol concentration suggest that the structural processes occurring in this system are caused by dimerization of the solute molecules.
7
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Structure of Aqueous Solutions of Tetramethylammonium Chloride Investigated by Positron Annihilation and Ultrasonic Methods

52%
Jákli G., Jerie K., Baranowski A., Gliński J.
Acta Physica Polonica A
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1998
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vol. 93
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issue 4
649-658
EN
The structure of aqueous solutions of tetramethylammonium chloride was investigated using sound velocity and positron annihilation methods. The results are different than those obtained earlier for systems where hydrophobic hydration occurs, although some evidences for formation of clathrate-like hydrates in liquid phase were observed. The results are interpreted, among others, in terms of competition of different hydrates of tetraalkylammonium cations, hydration of chloride anions, and formation of ionic pairs.
8
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Structure of Cyclohexane + t-Butanol Mixtures from Positron Annihilation and Ultrasonic Velocity Measurements

52%
Jerie K., Baranowski A., Gliński J.
Acta Physica Polonica A
|
1993
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vol. 83
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issue 3
321-326
EN
The densities of and sound velocities in t-butyl alcohol solutions in cyclohexane were determined in the temperature range 25 to 45°C. From these data adiabatic compressibility coefficients of the solutions were calculated, as well as excess densities and compressibilities. The positron annihilation spectra of the solutions were measured at room temperature. The results plotted against alcohol concentration show structural processes, which can be attributed to dimerization of the solute molecules.
9
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Positron Annihilation in and Adiabatic Compressibility of Ethylene Glycol Aqueous Solutions

52%
Baranowski A., Jerie K., Gliński J., Orzechowski K.
Acta Physica Polonica A
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1995
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vol. 88
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issue 1
59-66
EN
The positron annihilation lifetime and ultrasonic velocity in aqueous ethylene glycol solutions were measured. A comparison between the concen­tration and temperature dependences of the above parameters suggests that there is a competition of hydrophobic (interstitial) and hydrophylic (substi­tutional) hydration.
10
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Positron Annihilation in and Compressibility of Water-Organic Solutions. The System Water-Pyridine

52%
Jerie K., Baranowski A., Gliński J., Jeżowska-Trzebiatowska B.
Acta Physica Polonica A
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1992
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vol. 82
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issue 3
471-479
EN
The results of positron lifetime and ultrasonic velocity measurements in dilute aqueous pyridine (PYR) solutions show unusual changes in ultrasonic, annihilation data in function of pyridine concentration. The results obtained suggest that strong structural changes occur in the system, in the region of low pyridine concentrations. Liquid clathrate hydrates forming in the system are supposed with unusual stoichiometry and untypical geometry. They are supposed to be very short-living and/or unstable.
11
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Structure of Aqueous Solutions of 1,2- and 1,3-Propanediol Investigated by Positron Annihilation and Ultrasonic Methods

52%
Jerie K., Baranowski A., Gliński J., Orzechowski K.
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vol. 95
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issue 4
562-567
EN
The structure of aqueous solutions of 1,2-propanediol and 1,3-propane-diol was investigated using adiabatic compressibility measurements and positron annihilation methods. The experimental results are different than those obtained earlier for systems where hydrophobic hydration dominates. There are some evidences for increased rigidity of the water network, which can arise from the formation of hydrogen bonds between diols and water.
12
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Annihilation of o-Positronium in the Vicinity of the Critical Mixing Point

52%
Jerie K., Baranowski A., Gliński J., Orzechowski K.
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vol. 95
|
issue 4
569-574
EN
Positron annihilation spectra were investigated in the critical region close to the consolute point of ethanol + dodecane mixture. The anomalies of the positron lifetimes and intensities were small, nevertheless it was found that the intensity of short-living components of annihilation spectrum seems to increase close to the critical temperature.
13
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Hydrophobic-Like Solvation in Non-Aqueous Solutions: Positron Annihilation in and Compressibility of Tert-butanol and Tetramethylurea in Ethylene Glycol

52%
Jerie K., Baranowski A., Gliński J., Przybylski J.
Acta Physica Polonica A
|
2001
|
vol. 99
|
issue 3-4
385-392
EN
The pioneer experimental results of positron annihilation experiments in non-aqueous solutions of tetramethylurea and tert-butanol were compared to those of ultrasonic velocity. For tert-butanol, the positron annihilation results exclude existence of hydrophobic-like interactions and formation of weak, labile crystalline-like solvates in solution. For tetramethylurea solute the changes of annihilation parameters with concentration are minor and only limited conclusions can be drawn on this system, while they are stronger for tert-butanol solute. However, all the above is consistent with an assumption that the more hydrophobic solute (tert-butanol) should affect the original glycol structure stronger than that interacting with glycol via hydrogen bondings only. On the other hand, the ultrasonic data for the systems tested, although very precise, hardly confirm formation of any specific structure. It is possible, however, that the solvates do not differ in their compressibility from the pure liquids, and/or are formed only in very small amounts. Thus, usefulness of the positron annihilation method in investigation of liquid structure was proven.
14
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Studying of Nickel Alloys with 1 at.% of Ge, Zn, In, Zr and Pb by Positron Annihilation Methods

52%
Baranowski A., Kostrzewa M., Szuszkiewicz M.
Acta Physica Polonica A
|
2001
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vol. 99
|
issue 3-4
329-336
EN
The measurements of cold rolled nickel alloys with 1 at.% of Ge, Zn, In, Zr, Pb and additionally Ti and Sb by positron lifetime and Doppler broadening techniques have been done. Monovacancies were a dominating type of defects in the alloys. The authors of the present paper connect the differences between the annihilation parameters of the investigated samples with the existence of the vacancy-impurity atom pairs. A direct proportionality between the vacancy lifetime and the product of vacancy-impurity binding energy and atomic radius of impurity atom has been found.
15
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Positron Annihilation with Electrons of Admixture Atoms in Some Binary Nickel Alloys

52%
Baranowski A., Kostrzewa M., Szuszkiewicz M.
|
EN
Weighted difference curves have been shortly presented as a proper tool allowing to analyze in another way two-detector Doppler spectra regarding positron annihilation with admixture electrons in some nickel alloys. The analysis of low and middle momentum parts of Doppler spectra for investigated alloys reflects the annihilation of positrons with admixture electrons. There is no distinct signal of annihilations with admixture electrons from the positron lifetime data for well-annealed samples.
16
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Positron Annihilation in and Compressibility of Water-Organic Mixtures. The System Water-Formamide

52%
Jerie K., Baranowski A., Gliński J., Orzechowski K.
Acta Physica Polonica A
|
1994
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vol. 85
|
issue 3
563-569
EN
The experimental results of positron annihilation experiments in aqueous solutions of formamide were compared to those of ultrasonic velocity. The systems under investigation behave untypically while changing formamide concentration. The results are explained in terms of hydrophilic hydration and lack of hydrophobic interactions.
17
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Positron Annihilation in and Adiabatic Compressibility of Water-Organic Solutions. The System Water-Dimethylsulfoxide

45%
Jerie K., Baranowski A., Rozenfeld B., Jeżowska-Trzebiatowska B., Gliński J.
Acta Physica Polonica A
|
1991
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vol. 79
|
issue 4
507-515
EN
The results of positron lifetime and ultrasonic velocity measurements in dilute aqueous dimethylsulfoxide (DMSO) solutions show the usual extreme characteristic for polar organic solutes. The results obtained suggest that strong structural changes occur in the system, in the region of low DMSO concentrations. Liquid clathrate hydrates forming in the system are supposed, with unusual stoichiometry and untypical geometry of the hydrates.
18
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Structure of Aqueous Solutions of Acetonitrile Investigated by Acoustic and Positron Annihilation Measurements

45%
Jerie K., Baranowski A., Koziol S., Gliński J., Burakowski A.
Acta Physica Polonica A
|
2005
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vol. 107
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issue 5
826-831
EN
We report the results of acoustic and positron annihilation measurements in aqueous solutions of acetonitrile (CH_3CN). Hydrophobicity of the solute is discussed, as well as the possibility of describing the title system in terms of hydrophobic solvation. The concept of Levay et al. of calculating the "ideal positronium lifetimes is applied, basing on the mean volume of cavities (holes) in liquid structure available for positronium pseudoatom. The same calculations performed using the Tao model of annihilation yield very different results. It can be concluded that either acetonitrile forms with water clathrate-like hydrates of untypical architecture, or it is too weak hydrophobic agent to form clathrate-like hydrates at all. The former interpretation seems to be more probable.
19
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Ultramarine, Lazurite and Sodalite Studied by Positron Annihilation and EPR Methods

45%
Baranowski A., Dębowska M., Jerie K., Jezierski A., Sachanbiński M.
Acta Physica Polonica A
|
1995
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vol. 88
|
issue 1
29-41
EN
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.
20
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Structure of Aqueous Solutions of 1,2-, 1,3- and 1,4-Butanediol Investigated by Positron Annihilation and Ultrasonic Methods

45%
Jerie K., Baranowski A., Gliński J., Orzechowski K., Przybylski J.
Acta Physica Polonica A
|
2001
|
vol. 99
|
issue 3-4
393-398
EN
The structure of aqueous solutions of 1,2-, 1,3- and 1,4-butanediol was investigated using adiabatic compressibility measurements and positron annihilation methods. In the case of 1,2-butanediol the experimental results are very similar to those obtained earlier for systems where hydrophobic hydration dominates. In other cases there are evidences for increased rigidity of the water network, which arises from formation of hydrogen bonds between diols and water. Usefulness of both the methods applied in investigating the structure of liquid solutions was proved.
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