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Wyszukujesz frazę "79.90.+B" wg kryterium: Temat


Wyświetlanie 1-6 z 6
Tytuł:
Thermal Desorption of Potassium from Clean and Sulfur Covered Nickel
Autorzy:
Błaszczyszyn, R.
Błaszczyszynowa, M.
Gubernator, W.
Powiązania:
https://bibliotekanauki.pl/articles/1943955.pdf
Data publikacji:
1995-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.90.+b
73.30.+y
79.60.Dp
Opis:
Activation energy for thermal desorption of potassium from clean and sulfur covered surfaces of nickel was determined by means of the field emission method. For the low potassium coverage limit (Θ$\text{}_{K}$ ≈ 0.02) the desorption was detected from the whole emitter surface in the temperature range of 825-1000 K for the atoms and of 725-825 K for the species of atoms and ions of the potassium. The activation energies of neutral desorption were found to be E$\text{}_{Ni}^{a}$ = 3.8 eV for the clean nickel and E$\text{}_{S}\text{}_{/}\text{}_{Ni}^{a}$ = 3.0 eV for the sulfur covered nickel, Θ$\text{}_{s}$ ≈ 0.5. The activation energies for the desorption of the species of atoms and ions increased from E$\text{}_{Ni}^{a+i}$ = 2.5 eV for the clean nickel to E$\text{}_{S}\text{}_{/}\text{}_{Ni}^{a+i}$ = 2.9 eV for the sulfur covered nickel Θ$\text{}_{s}$ ≈ 0.5. Also, a value of E$\text{}_{S'}\text{}_{/}\text{}_{Ni}^{a+i}$ = 4.1 eV was found for a higher coverage of sulfur, Θ$\text{}_{s}$ ≈ 1. The results are discussed in terms of Gurney model.
Źródło:
Acta Physica Polonica A; 1995, 88, 6; 1151-1160
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Adsorption of H$\text{}_{2}$O on Pt Field Emitter: Surface Diffusion and Field-Induced Effects
Autorzy:
Blaszczyszynowa, M.
Błaszczyszyn, R.
Bryl, R.
Powiązania:
https://bibliotekanauki.pl/articles/1933649.pdf
Data publikacji:
1995-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.90.+b
68.35.Fx
79.70.+q
Opis:
Adsorption of an Η$\text{}_{2}$O layer onto a Pt field emitter tip under the influence of an electric field and the surface diffusion of water were studied by using the field electron microscopy method. The presence of a negative field (field electron microscopy mode of operation), examined in the range of 33-44 MV/cm, significantly reduced the water coverage on the emitter at temperatures above 120 K. The reduction could also occur upon drawing a high density field emission current when the emitter was kept at 78 K. Surface diffusion of water, which was observed in the temperature range 120-132 K, corresponded to the "unrolling the carpet" mechanism and started from a water multilayer to a surface region water- and/or hydrogen-submonolayer covered. This was accompanied by the transition process from the state of the current- and field-induced redistribution of Η$\text{}_{2}$O to the state of thermal equilibrium. The activation energy of the diffusion was found to be 19 and 25 kJ/mol depending on the crystallographic direction. A positive electric field of 44 MV/cm, which was applied at temperatures of the substrate in excess of 121 K, decreased the field emission of the system and raised the desorption temperature of the layer over 720 K. It is assumed that the negative electric field causes reorientation of Η$\text{}_{2}$O molecules at the surface of platinum tip. The positive as well as negative electric fields promote the field desorption of water, which is in accordance with the results reported before.
Źródło:
Acta Physica Polonica A; 1995, 88, 3; 511-526
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Diffusion of Potassium on Nickel
Autorzy:
Błaszczyszynowa, M.
Błaszczyszyn, R.
Powiązania:
https://bibliotekanauki.pl/articles/1892562.pdf
Data publikacji:
1992-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.35.Fx
79.70.+g
79.90.+b
Opis:
The surface diffusion of a potassium dose corresponding to the average coverage Θ̅$\text{}_{K}$ = 1.5 on nickel was studied using the field emission technique in the temperature range of 78-133 K. In general, under such conditions diffusion proceeds with the sharp moving boundary and the activation energy Q from 0.16 eV to 0.36 eV dependently on the crystallographic directions. Free boundary migration with the energy Q < 0.16 eV is expected on the close-packed regions {111} and {001} already at liquid N$\text{}_{2}$ temperature. The results are discussed in relation to the atomic structure of the nickel substrate taking into account the interaction in the adsorption layer.
Źródło:
Acta Physica Polonica A; 1992, 81, 2; 285-294
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Environment of Air-Ions in Healing Chambers in the "Wieliczka" Salt Mine
Autorzy:
Wiszniewski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1400509.pdf
Data publikacji:
2015-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.90.+B
82.30.Fi
61.80.Jh
Opis:
The present paper is an attempt to determine the parameters of air-ions in salt mines. The investigations were aimed at determination of the degree of ionization of air in places where cosmic ray particles do not arrive at. Specifically, measurements were performed in healing chambers in salt mines where establishment of standards in the healing process should be considered as the necessity. Preliminary investigations were carried out in three salt mines using the Gerdien ion counter, with sensitivity approximately of $20 ions/cm^{3}$. The studies have shown that concentrations of small air-ion are in the range of 1200-4700 ions/$cm^{3}$ and remain persistently in adits and medicinal chambers of this mine. It means that the air in the "Wieliczka" Salt Mine is several times more saturated with air-ions as compared to the neutral atmosphere background. According to the existing standards, this ionization level is not only deemed acceptable but also optimal for humans. Because results of unsystematic measurements of ion concentrations performed in different Polish salt mines are quite similar, it is assumed that the results presented in this paper are of universal character, and that comparable ionization level in the all mines would be expected. Due to this fact, it was decided that only one of them "Wieliczka" Salt Mine (Poland) can be selected for further detailed research.
Źródło:
Acta Physica Polonica A; 2015, 127, 6; 1661-1665
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Semiconductor Spintronics: Role of the Valence-Band Holes
Autorzy:
Dargys, A.
Powiązania:
https://bibliotekanauki.pl/articles/2041626.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.Jv
73.40.Gk
78.55.-m
79.90.+b
Opis:
Two aspects related to valence-band hole spin are considered: spin surfaces in p-type semiconductors and flipping of the hole spin by an ultrashort electric field pulse. It is shown that heavy, light, and split-off holes have different spin surfaces. In general, the shape of the surface in real semiconductors may depend on the hole wave vector direction and magnitude. The concept of spin surface is used to explain very strong anisotropy of hole spin injection efficiency observed recently in ferromagnetic-semiconductor structures and in optimizing ultrafast spin switching. It was shown that, of all spin flipping mechanisms, the most effective one is associated with hole transfer between different spin surfaces in high electric fields. The less effective mechanisms are related to valence band warping and nonparabolicity. Examples of the hole spin flipping dynamics and the discussion on ultrafast control of spin in semiconductors by π-type electrical pulses are presented.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 46-55
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Control of Valence-Band Hole Spin by Electric Field
Autorzy:
Dargys, A.
Powiązania:
https://bibliotekanauki.pl/articles/2037172.pdf
Data publikacji:
2004-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.Jv
73.40.Gk
78.55.-m
79.90.+b
Opis:
Coherent properties of the hole spin in an electric field are investigated. The tunneling between valence bands is used to control the transitions between the spin states. Extensive numerical studies using the time-dependent Schrödinger equation for valence band are presented to demonstrate the characteristic properties of the hole spin dynamics in dc, harmonic, as well as optimized electric fields for real valence bands of silicon. The paper also shows how one can connect the average hole spin with the initial hole wave function in the time-dependent Schrödinger equation.
Źródło:
Acta Physica Polonica A; 2004, 105, 3; 295-306
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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