Results 1 - 10 of 19
Results 1 - 10 of 19. Search took: 0.014 seconds
|Sort by: date | relevance|
[en] We have performed Monte-Carlo simulations of slow electrons impinging on semi-infinite aluminium and copper in the energy range 0.5-4 keV. We present results for the backscattering coefficients, mean penetration depths and stopping profiles. Our results for the backscattering coefficients agree well with the experimental data within the limits of the statistical accuracy. The slight discrepancy between simulated and experimental results regarding the mean penetration depth is discussed. (authors)
[en] Experimental ionization cross sections for K-shell by protons for elements from Be to U available in the literature from 1953 to 1999 are fitted to deduce the empirical K-shell ionization cross sections, 5400 values of cross sections have been collected from various references. The deduced empirical cross sections are compared to the experimental data and to the theoretical values obtained by our research group within the ECPSSR theory and also with the reference ionization cross sections obtained by Paul and Sacher [H. Paul and J. Sacher At. Data. Nucl. Data. Tables 42 (1989) 105]
[en] Theoretical M-shell X-ray production cross sections have been calculated within the ECPSSR model. The semi-empirical cross sections are then deduced by fitting the available experimental data normalized to their corresponding theoretical values for elements with 72≤ Z ≤ 90 by proton in the energy range 0.1-4.0 MeV. Also, an analytical formula has been used to calculate the empirical X-ray production cross sections by direct fitting of the same experimental data, which are found to be universal, both for individual and collective fits. On the other hand, based on the individual fitting which gives the reliable cross sections, we attempt to deduce another new empirical cross sections by assuming that the ratio empirical to ECPSSR of the cross sections is roughly the same for all elements. In addition, our results are presented for selected heavy elements, namely 74W, 79Au and 83Bi, being the most extensively studied. Finally, a comparison is made between the different procedures followed here and the experimental data
[en] Transparent zinc oxide (ZnO) thin films are fabricated by a simple sol-gel spin-coating technique on glass substrates with different solution concentrations (0.3–1.2 M) using zinc acetate dehydrate [Zn(CH 3 COO) 2·2H 2 O] as precursor and isopropanol and monoethanolamine (MEA) as solvent and stabilizer, respectively. The molar ratio of zinc acetate dehydrate to MEA is 1.0. X-ray diffraction, ultraviolet-visible spectroscopy and photoluminescence spectroscopy are employed to investigate the effect of solution concentration on the structural and optical properties of the ZnO thin films. The obtained results of all thin films are discussed in detail and are compared with other experimental data. (paper)
[en] A large database containing about 5400 experimental K-shell ionization cross-sections by protons for elements from Be to U is collected from various sources and compilations available in the literature from 1953 to 1999. The data are divided into groups corresponding to their atomic numbers and fitted separately by analytical functions to deduce empirical K-shell ionization cross-sections. The deduced empirical K-shell ionization cross-sections are presented together with the reference ones obtained by Paul and Sacher for selected elements [H. Paul, J. Sacher, At. Data Nucl. Data Tables 42 (1989) 105]. The two sets of results are compared to the calculations within the ECPSSR theory and discussed.
[en] In this paper, the measured K β /K α intensity ratio values published in the literature from 1980 to 2011 have been reported. The weighted- and unweighted-mean values of the experimental data were fitted by the analytical function to deduce new semiempirical and empirical intensity ratios in the atomic range of 16 Z 92. The semi-empirical intensity ratios were then deduced by fitting the experimental data normalized to their corre- sponding theoretical values and the experimental data were directly fitted to deduce the empirical ones. The results were compared with the other theoretical and experimental values reported in the literature
[en] In this study, empirical K-shell fluorescence yields (ωK) from the available experimental data for elements with 6≤Z≤99 were calculated. The experimental data are fitted using the quantity (ωK/(1-ωK))1/q (where q=3, 3.5 and 4) vs. Z to deduce the empirical fluorescence yields. A comparison is made between the results of the procedures followed here and the literature theoretical and empirical values.
[en] Structural, electronic and optical properties of ZnTe compound were calculated using Density Functional Theory (DFT) based on the pseudopotentials and planewaves (PP-PW) method as implemented in the ABINIT computer code, where the exchange–correlation functional is approximated using the local density approximation (LDA) and the generalized gradient approximation (GGA). The obtained results from either LDA or GGa calculation for lattice parameter, energy band gap and optical parameters, such as the fundamental absorption edge, the peaks observed in the imaginary part of the dielectric function, the macroscopic dielectric constants and the optical dielectric constant, are compared with the available theoretical results and experimental data
[en] Within the individual treatment of the elements from beryllium (4Be) to uranium (92U), the experimental databases are normalized to their corresponding values of the ECPSSR model to deduce the semi-empirical cross sections. These databases rely on the different compilations available in the literature and on the other data extracted from papers published from 1953 till 2010. In the present paper, a fourth order polynomial was used to fit very well the existing normalized database of K-shell ionization cross sections by proton. These procedures generate a new set of parameters for the sake of the quick calculation of the semi-empirical cross sections. A comparison is made between the deduced results and those obtained by using the ECPSSR model where a remarkable discrepancy is observed at low-proton velocity regime especially for the lightest elements
[en] The database, which relies on different compilations available in the literature and on other experimental values extracted from papers published from 1992 till 2010, is used, within the individual treatment of the elements from beryllium (4Be) to uranium (92U), to deduce the empirical cross sections. These experimental data can be presented in a single curve, depending on a scaling law extracted from studies in the most familiar theories of collision (PWBA and BEA). Then, a fourth order polynomial was used to fit very well the existing database of K-shell ionization cross sections by proton. This procedure generates a new set of parameters to calculate empirical cross sections. Following the present procedure, our results are compared with those obtained using the ECPSSR model where a discrepancy is observed in the low-proton energy regime. - Highlights: → We used the experimental data to define the K-shell ionization cross sections. → These values are presented in a single curve used PWBA and BEA theories. → The empirical values are defined for each element separately.