518 research outputs found
PHOTOIONIZATION CROSS-SECTION AND RESONANCE STRUCTURE OF ATOMIC SULFUR
No full textMany-body perturbation theory has been applied to calculate the partial and total photoionization cross sections for neutral sulphur from the first ionization threshold at 10.36 eV to 60 eV. The excitations from the ground state S(3s(2)3p4 3p), leaving the residual S+ ions in the lowest five LS states (3s(2)3p3 4S, 2D , 2P and 3s3p4 4p, 2P), are considered. The results are presented in both the dipole length and velocity forms. The threshold behaviour of the partial photoionization cross sections are found to be dominated by the overlapping autoionizing resonances converging to S+(3s(2)3p3 4S, 2D, 2P) and S+(3s3p4 4p, 2p) limits. The excited single-particle states are calculated in an effective single-particle potential which includes, in an approximate way, the effects of the interaction among many final channels. The results are compared with the previous photoionization studies of sulphur
Aggregation operators of complex fuzzy Z-number sets and their applications in multi-criteria decision making
No full textFuzzy sets (FSs) are a flexible and powerful tool for reasoning about uncertain situations that cannot be adequately expressed by classical sets. However, these sets fall short in two areas. The first is the reliability of this tool. Z-numbers are an extension of fuzzy numbers that improve the representation of uncertainty by combining two important components: restriction and reliability. The second is the problems that need to be solved simultaneously. Complex fuzzy sets (CFSs) overcome this problem by adding a second dimension to fuzzy numbers and simultaneously adding connected elements to the solution. However, they are insufficient when it comes to problems involving these two areas. We cannot express real-life problems that need to be solved at the same time and require the reliability of the information given with any set approach given in the literature. Therefore, in this study, we propose the complex fuzzy Z-number set (CFZNS), a generalization of Z-numbers and CFS, which fills this gap. We provide the operational laws of CFZNS along with some properties. Additionally, we define two essential aggregation operators called complex fuzzy Z-number weighted averaging (CFZNWA) and complex fuzzy Z-number weighted geometric (CFZNWG) operators. Then, we present an illustrative example to demonstrate the proficiency and superiority of the proposed approach. Thus, we process multiple fuzzy expressions simultaneously and take into account the reliability of these fuzzy expressions in applications. Furthermore, we compare the results with the existing set operations to confirm the advantages and demonstrate the efficiency of the proposed approach. Considering the simultaneous expression of fuzzy statements, this study can serve as a foundation for new aggregation operators and decision-making problems and can be extended to many new applications such as pattern recognition and clustering
Application of the Leray-Schauder alternative to nonlinear singular operator equations
No full textAltun, Ishak/0000-0002-7967-0554In this paper, we study the problem of existence of solution of nonlinear singular integral equations of the form {w(z) = Phi(z) + T(G)F (., w (.), h (.)) (z) h(z) = Phi'(z) + Pi(G)F (., w (.), h (.)) (z), z is an element of G subset of C. (C) 2009 Elsevier Ltd. All rights reserved
Enhancement of high-order harmonic generation in the presence of noise
No full textWe report on our simulations of the generation of high-order harmonics from atoms driven by an intense femtosecond laser field in the presence of noise. We numerically solve the non-perturbative stochastic time-dependent Schrodinger equation and observe how varying noise levels affect the frequency components of the high harmonic spectrum. Our calculations show that when an optimum amount of noise is present in the driving laser field, roughly a factor of 45 net enhancement can be achieved in high-order harmonic yield, especially, around the cut-off region. We observe that, for a relatively weak noise, the enhancement mechanism is sensitive to the carrier-envelope phase. We also investigate the possibility of generating ultra-short intense attosecond pulses by combining the laser field and noise and observe that a roughly four orders of magnitude enhanced isolated attosecond burst can be generated
Level-resolved distorted-wave cross-sections of electron impact ionization of Ar5+
No full textElectron impact ionization cross sections of Ar5+ were calculated using configuration-average (CADW) and level-resolved (LRDW) distorted-wave methods. Direct ionization cross-sections of 2s, 2p, 3s and 3p subshells were calculated within a CADW approximation. The contributions from the excitation autoionization channels were evaluated assuming single excitations from the 2s, 2p, and 3s subshells and in both CADW and LRDW methods. The radiative stabilization of the excitation autoionization channels were found to reduce the excitation autoionization by a small amount. © 2009 IOP Publishing Ltd
Dielectronic recombination data for dynamic finite-density plasmas - XI. The sodium isoelectronic sequence
No full textDielectronic recombination (DR) rate coefficients for 22 sodium-like ions, between Mg+ and Xe43+, forming magnesium-like ions have been calculated as part of the assembly of a level-resolved DR database necessary for modelling dynamic finite-density plasmas, within the generalized collisional - radiative framework. Calculations have been performed from both ground and metastable initial states, in both LS - and intermediate coupling, allowing for Delta n = 0 and Delta n = 1 core-excitations from ground and metastable levels. Partial and total DR coefficients have been calculated for Mg+ to Zn19+, as well as Kr25+, Mo31+, and Xe43+. Results for a selection of ions from the sequence are discussed in the paper and compared with existing theoretical and experimental results. A full set of results can be accessed from the Atomic Data and Analysis Structure (ADAS) database or from the Oak Ridge Controlled Fusion Atomic Data Center (http:// www-cfadc.phy.ornl.gov/data_and_codes)
Dielectronic recombination data for dynamic finite-density plasmas - VI. The boron isoelectronic sequence
No full textWe have calculated dielectronic recombination rate coefficients for 22 ions of the boron isoelectronic sequence, between C+ and Xe49+, within the generalized collisional-radiative framework, as outlined by Badnell et al. (2003). Calculations have been performed from both ground and metastable initial states, in both LS- and intermediate-coupling, allowing for Deltan = 0 and Deltan = 1 core-excitations. Results are presented and discussed for a selection of ions from the sequence. Results which are not presented here can be accessed from the Atomic Data and Analysis Structure (ADAS) database (Summers 2003) or from the Oak Ridge Controlled Fusion Atomic Data Center (http://www-cfadc.phy.ornl.gov). Comparison is made with the results of other existing theoretical calculations
Determination of the recombination rate coefficients for Na-like SiIV forming Mg-like SiIII
No full textAims. Absolute, total recombination rate coefficients for Si IV were determined using the CRYING heavy-ion storage ring. Calculated rate coefficients were used to estimate recombination into states that could not be detected in the experiment because of field ionization. Total, as well as separate, radiative and dielectronic plasma recombination rate coefficients were determined. Methods. Stored ions were merged with an expanded electron beam in the electron cooler section of the storage ring. Recombined ions were separated from the stored ion beam in the first dipole magnet after the electron cooler and were detected with unity efficiency. The absolute radiative and dielectronic recombination rate coefficients were obtained over a center-of-mass energy range of 0-20 eV, covering. Delta n = 0 core excitations up to the 3s -> 3d series limit. The results of an intermediate coupling AUTOSTRUCTURE calculation were compared with the experiment. The theoretical results were also used to estimate the contribution to dielectronic recombination by high Rydberg states, which were not detected because of field ionization. The spectra were convoluted with Maxwell-Boltzmann energy distributions in the 10(3)-10(6) K temperature range. Results. The resulting plasma recombination rate coefficients are presented and compared with theoretical results frequently used for plasma modeling. In the 10(3)-10(4) K range, a significant underestimation of the calculated dielectronic recombination plasma rate coefficients was observed. Above 3 x 104 K, the agreement between our dielectronic recombination plasma rate coefficients and two of the previously published rate coefficients is better than 20%. Conclusions. The observed differences between the experimental and calculated recombination rate coefficients at low temperatures reflect the need for benchmarking experiments. Our experimentally-derived rate coefficients can guide the development of better theoretical models and lead to more accurately-calculated rate coefficients
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