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Wyszukujesz frazę "positron" wg kryterium: Wszystkie pola


Tytuł:
"Ridge" Fermi Surface Study in Metallic (R)Ba$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-δ}$ (R = Y, Dy) and in Oxygen Deficient YBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-δ}$ by Positron Annihilation
Autorzy:
Hoffmann, L.
Manuel, Α. A.
Barbiellini, B.
Peter, Μ.
Shukla, A.
Walker, E.
Powiązania:
https://bibliotekanauki.pl/articles/1933509.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.Jt
74.72.Βk
71.25.Ηc
78.70.Bj
Opis:
We present a detailed positron 2D-ACAR measurements study of the "ridge" Fermi surface of (R)Ba$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-δ}$ (R = Y, Dy) compared to full-potential linearized augmented plane wave and linear muffin-tin orbital calculations. From different 2D-ACAR projections measured in DyBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-δ}$, a 3D model of the momentum density of the ridge was established and is in good agreement with LMTO calculations of YΒa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7}$, confirming the description of the ridge Fermi surface by local density approximation calculations. The ridge is also studied in oxygen deficient YΒa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-δ}$. With growing δ, the ridge disappears without changing in width. This is consistent with full-potential linearized augmented plane wave calculations of YΒa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{6.5}$, and supports the phase separation model of Mesot et al.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 147-161
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
80 Years of Positron Annihilation Radiation
Autorzy:
Goworek, T.
Powiązania:
https://bibliotekanauki.pl/articles/1339289.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
01.65.+g
Opis:
Short history of the investigations of annihilation radiation is presented, from early experiments with ThC" to the introduction of two main methods: angular correlation of annihilation quanta and positron lifetime spectroscopy.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 685-687
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Comparison of Different Theoretical Models of Positron Lifetime Spectra for Polymers
Autorzy:
Kansy, J.
Powiązania:
https://bibliotekanauki.pl/articles/1812531.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The same reference positron lifetime spectra of polyurethane, measured in temperature range 112 to 390 K, were analyzed with three theoretical models: the "conventional" model with three exponential decay component of discrete values of lifetimes, a model with one discrete exponential component and two "packages" of exponentials with log-normal distribution of annihilation rates, and a model considering positronium slow localization, positronium internal relaxation as well as "delayed" formation of positronium. It turns out that the two latter models fit to the experimental data with the same excellent quality, in spite of the fact that in both models the ratio of intensities related to para-positronium and ortho-positronium was constrained to be as 1:3.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1397-1407
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Magnetically Guided Slow Positron Beam for Defect Studies
Autorzy:
Anwand, W.
Kissener, H.
Brauer, G.
Powiązania:
https://bibliotekanauki.pl/articles/1933460.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
06.90.+v
07.90.+c
Opis:
The design and construction of a compact, magnetically guided slow positron beam is discussed. The system uses a 30 mCi $\text{}^{22}$Νa source. It consists of three main parts: (i) the source chamber with a tungsten foil transmission moderator and the extraction optics, (ii) the beam line with magnetic beam guidance, a bent tube for the separation of the fast positrons and the accelerator stage, (iii) the target chamber with the sample holder and the detector electronics. The energy of the incident positrons can be varied from 30 eV up to 50 keV. Furthermore source geometries, pre-acceleration, main acceleration sections and various magnetic induction profiles have been considered, such as (i) rectangular, conical and bent Wehnelt electrodes, (iii) pre-accelerator voltage shared over several electrodes, (iii) weak, strong, constant and z-dependent B-profiles, (iv) geometric options in the main accelerator region, (v) purely electrostatic and combined electric/magnetic fields. The beam is mainly designed for defect profile studies in ultra high vacuum conditions.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 7-11
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new approach to the presentation of the positron annihilation lifetime spectroscopy results, n-alkanes
Autorzy:
Zgardzińska, B.
Standzikowski, K.
Powiązania:
https://bibliotekanauki.pl/articles/1057935.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
82.30.Gg
Opis:
The standard form of the positron annihilation lifetime spectroscopy results presentation are two plots of o-Ps lifetime and intensity as a function of external factor, e.g. temperature, pressure. Both o-Ps parameters change (stepwise) when in the medium phase transitions occur. For a more complete picture of the structural changes occurring in the matter we suggest to use an additional plot, in the coordinates, (τ₃, I₃). The hydrocarbons are selected to show the advantages following from the presentation of the results in the intensity-lifetime (INTI) plot.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1496-1500
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Study of Defects in Iron Based Alloys by Positron Annihilation Techniques
Autorzy:
Mostafa, K.
De Baerdemaeker, J.
Segers, D.
Calvillo, P.
Van Caenegem, N.
Houbaert, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1812543.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
62.20.F-
Opis:
Defects in different iron based alloys were studied at room temperature using positron annihilation techniques. In FeSi alloys, it was found that the Si content and the deformation temperature affect the positron annihilation parameters. In Fe-Mn-Si-Cr-Ni-C samples with different deformations, positron lifetime measurements were carried out before and after isochronal annealing. X-ray diffraction gave information about the different microstructural phases that exist in the deformed alloys before and after annealing. During deformation a martensiticεphase is induced. At 500°C, defects and theεmartensite phase were almost annealed out from the low deformed samples.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1471-1478
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Study of Positron Properties in Quartz Crystals and Synthetic Silica Glass
Autorzy:
Anwand, W.
Brauer, G.
Hasegawa, M.
Dersch, O.
Rauch, F.
Powiązania:
https://bibliotekanauki.pl/articles/2024077.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
The monoenergetic positron beamline "SPONSOR" at Rossendorf has been used to investigate the positron behaviour in a naturally grown Brasilian quartz, two synthetic quartz crystals of different origin, and synthetic silica glass. The measurements allow us to obtain the positron diffusion length of free positrons and Bloch para-positronium, if formed, in these materials. In addition, hydrothermal treatment of a synthetic quartz has been used to introduce hydrogen into the crystal up to a certain depth. The presence of hydrogen is found to influence the formation of para-positronium. The depth distribution of hydrogen has been measured independently by nuclear reaction analysis, and will be discussed in comparison with the results deduced from the positron studies.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 321-328
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Algorithm for Shifting Positron Annihilation Spectra
Autorzy:
Dryzek, J.
Polak, A.
Powiązania:
https://bibliotekanauki.pl/articles/2024230.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
We present a simple procedure which allows us to shift the positron annihilation spectra, e.g., the Doppler broadening spectrum of the annihilation line. That is especially required when we wish to compare different spectra obtained with a spectrometer with the reduction of background. As an application of the obtained algorithm we present the studies of positron annihilation in carbon material samples.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 355-361
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Attempt to Produce the Implanted $\text{}^{22}$Na Source for Positron Spectrometry
Autorzy:
Latuszyński, A.
Yushkevich, Yu. V.
Bystrov, V. A.
Misak, R.
Wawryszczuk, J.
Goworek, T.
Powiązania:
https://bibliotekanauki.pl/articles/1929102.pdf
Data publikacji:
1993-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
28.60.+s
29.25.Rm
Opis:
Preliminary results of $\text{}^{22}$Na implantation into the metal foils in order to produce the positron source for annihilation experiments are presented.
Źródło:
Acta Physica Polonica A; 1993, 83, 3; 345-348
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analiza porównawcza struktury wewnętrznej implantów hydrofilowych oraz hydrofobowych stosowanych w chirurgii okulistycznej metodą spektroskopii czasów życia pozytonów
Comparative analysis of internal structures of hydrophilic and hydrophobic implants applied in ophthalmology by means of positron annihilation lifetime spectroscopy
Autorzy:
Chamerski, K.
Powiązania:
https://bibliotekanauki.pl/articles/134780.pdf
Data publikacji:
2015
Wydawca:
ADVSEO
Tematy:
soczewki wewnątrzgałkowe
anihilacja pozytonów
wolna objętość
wielozadaniowość
hydrofilowość
hydrofobowość
chromofory
intraocular lenses
positron annihilation
free volume
multivacancies
hydrophilicity
hydrophobicity
chromophores
Opis:
In presented work internal structures of intraocular lenses were analyzed in terms of defectiveness degree. Studies were conducted by means of positron annihilation lifetime spectroscopy method PALS. The aim of the work was determination of basic parameters describing annihilation centers in research materials, such as positron lifetime in bulk material, mean positron lifetime in the internal structure, positron trapping rate by trapping centers as well as free volumes dimensions. In obtained results differences in free volumes and positron traps concentrations between hydrophilic and hydrophobic materials were noted. Furthermore, comparison of materials with and without blue light chromophores revealed differences in positron trapping rate by multivacancy-like free spaces. Achieved results were referenced for mechanical properties of the studied materials.
Źródło:
Technical Issues; 2015, 3; 3-10
2392-3954
Pojawia się w:
Technical Issues
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of free volumes and light transmission in hydrogel and silicone-hydrogel polymer contact lenses
Autorzy:
Kocela, A.
Miedzinski, R.
Filipecka, K.
Filipecki, J.
Powiązania:
https://bibliotekanauki.pl/articles/173601.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
positron annihilation
UV-vis-NIR
polymers
contact lenses
free volume
Opis:
The free volume holes and light transmission of hydrogel and silicone-hydrogel polymer contact lenses were investigated. As the material, the Proclear family (omafilcon A) of hydrogel contact lenses and the Biofinity family (comfilcon A) of silicone-hydrogel contact lenses were used. Positron annihilation lifetime spectroscopy was used to characterize geometrical sizes and fractions of the free volume holes in the investigated samples. There was a clear difference in the size of free volume holes and the fractional free volume between silicone-hydrogel and hydrogel polymer contact lenses. These changes are shown by a thorough analysis of the long-lived component of lifetime of ortho-positronium. At the same time, UV-vis-NIR in the spectral range 200-1000 nm studies were performed on the same samples of contact lenses spectrometry.
Źródło:
Optica Applicata; 2016, 46, 1; 35-45
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Annealing behaviour of plastically deformed stainless steel 1.4307 studied by positron annihilation methods
Autorzy:
Dryzek, E.
Sarnek, M.
Siemek, K.
Powiązania:
https://bibliotekanauki.pl/articles/148014.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
plastic deformation
positron annihilation
stainless steel
Opis:
Isochronal and isothermal annealing of stainless steel 1.4307 samples deformed by compression were investigated using Doppler broadening measurements of the annihilation line. We made an attempt to describe the obtained dependencies in terms of vacancy migration and sinking to the grain boundaries. The model assumed spherical grains with a homogeneous initial distribution of vacancies. The model was capable of following the isochronal annealing data quite accurately. However, the obtained activation energy of vacancy migration equal to 0.44 plus or minus 0.05 eV seemed too low. The isothermal annealing dependency was reproduced less precisely. The reason for this may be the presence of the alfa'-martensite particles in the samples, which can introduce additional defects seen by positrons in the temperature range in which the martensite reversion takes place.
Źródło:
Nukleonika; 2013, 58, 1; 215-219
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Antihydrogen Formation in Low Energy Collision of Positron with Antiproton
Autorzy:
Bhattacharyya, S.
Powiązania:
https://bibliotekanauki.pl/articles/1931542.pdf
Data publikacji:
1994-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
34.50.+a
34.70.+e
39.10.+x
Opis:
In the present paper two-body radiative recombination rate for the production of antihydrogen (H̅) in a merged beam of slow positrons (e$\text{}^{+}$) and antiprotons (p¯) is studied in the light of a two-step process, which consists of capture in an excited state of H̅ with subsequent decay to the ground state and emission of a photon. Computation is done using the field theory and the Coulomb gauge. Importance of the two-step radiative recombination process relative to the well-known spontaneous photorecombination process, on the two-body radiative recombination rate for antihydrogen formation, is discussed. The present result predicts higher contribution from the two-step radiative recombination process as compared to the spontaneous photorecombination process to the rate of cold antihydrogen formation with the relative collision energy below 0.01 Rydberg, near which experiments are being conducted. However, above 0.1 Rydberg the spontaneous photorecombination process dominates over the two-step radiative recombination process. The present result is valid, as well, for the formation of hydrogen atom due to collision between slow electron and proton.
Źródło:
Acta Physica Polonica A; 1994, 86, 3; 297-308
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of a Pulsed Slow-Positron Beam to Low-Density Polyethylene Film
Autorzy:
Hamada, E.
Oshima, N.
Katoh, K.
Suzuki, T.
Kobayashi, H.
Kondo, K.
Kanazawa, I.
Ito, Y.
Powiązania:
https://bibliotekanauki.pl/articles/2024257.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
A pulsing system for a slow-positron beam was applied to study the region near the surface of low-density polyethylene film using positron-annihilation lifetime measurement. The lifetime and intensity of ortho-positronium near the surface were measured as a function of the incident positron energy (1.6-9.1 keV). The size of intermolecular spaces in the surface region (~ 1500 nm) was larger than that in the bulk region. This tendency was especially strong in the region around 200 nm below the surface. On the other hand, the intensity of ortho-positronium decreased at lower incident positron energies, which was attributed to a decrease in the density of the spur electrons and/or an increase in the number of reemitted positrons from the surface.
Źródło:
Acta Physica Polonica A; 2001, 99, 3-4; 373-378
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of Positron Spectroscopy for the Detection of Nanostructures in Water-Alcohol Mixtures
Autorzy:
Stepanov, P.
Byakov, V.
Zaluzhnyi, A.
Powiązania:
https://bibliotekanauki.pl/articles/1338564.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.20.-w
82.20.Pm
82.30.Gg
82.80.Ej
Opis:
Analysis of the o-Ps lifetimes concentration dependences in water-propanol mixtures (with and without $CoCl_2$ additive) shows that this mixture looks like an emulsion of alcohol micelles in water at propanol mole fractions 0.1-0.4.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 767-769
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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