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[en] The structure fine constant (α) plays an important role in relativity, quantum physics and electromagnetism. It characterizes the strength of interaction between light and matter as described in the quantum electromagnetic theory. The fact that the value of the inverse of α nears an integer (137) has raised a lot of speculations. According to the Dirac theory, 1/α represents the limit of Z for elements: elements whose atomic number is over 137 cannot exist. Initially α represents the ratio between the electron speed on the first orbit of the relativistic Bohr atom and the speed of light: α = e2/(4*π*ε0*ℎ*c) where e is the elementary charge and ε the vacuum permittivity. The most accurate value of α obtained so far is α = 1/137035999037 (91), its measurement was based on the trapping of ultra-cold rubidium atoms. Recent studies on quasar spectra have shown that the α constant has changed by less than 1/10.000 of percent in 10 billion years. (A.C.)
[en] The high resolution near edge X-ray absorption fine structure spectrum of nitrogen displays the vibrational structure of the core-excited states. This makes nitrogen well suited for assessing the accuracy of different electronic structure methods for core excitations. We report high resolution experimental measurements performed at the SOLEIL synchrotron facility. These are compared with theoretical spectra calculated using coupled cluster theory and algebraic diagrammatic construction theory. The coupled cluster singles and doubles with perturbative triples model known as CC3 is shown to accurately reproduce the experimental excitation energies as well as the spacing of the vibrational transitions. In conclusion, the computational results are also shown to be systematically improved within the coupled cluster hierarchy, with the coupled cluster singles, doubles, triples, and quadruples method faithfully reproducing the experimental vibrational structure.
[en] Highlights: • The PaSR-based soot model proposed by the authors’ group has been further improved. • The present model is physically more sound. • The improved model has been implemented into the in-house version of the FireFOAM code. • New formulas have been proposed to compute characteristic time for soot formation and oxidation. • The predictions have achieved improved agreement with the experimental measurements. - Abstract: The extension of the laminar smoke point based approach to turbulent combustion using the partially stirred reactor (PaSR) concept proposed by Chen et al. (2014) has been further improved to overcome the limitation in the formulations of Chen et al. (2014) which assumed infinitely fast soot oxidation chemistry and constant soot formation characteristic time. In the PaSR approach, each computational cell is split into two zones: the reacting zone and the non-reacting zone. Soot formation and oxidation are assumed to take place at finite rates in the reacting zone and computed from the corresponding laminar rates and the mass fractions for soot formation and oxidation, which are evaluated in each computational cell from the characteristic time scales for turbulent mixing, soot formation and oxidation. Since soot would be produced in not only the fine structures but also surrounding fluids in the Eddy-Dissipation-Concept (EDC) model, the average field parameters between the fine structure and surrounding fluid are employed instead of those Favre-averaged values in Chen et al.’s soot formation model. The newly extended model has been implemented in FireFOAM, a large eddy simulation (LES) based solver for fire simulation based on the open source CFD code OpenFOAM®. Numerical simulations of a 30 cm diameter heptane and toluene pool fires tested by Klassen and Gore (1992) were performed for validation. The predicted soot volume fraction and temperature have achieved improved agreement with the experimental measurements in comparison with that of Chen et al. (2014), demonstrating the potential of the improved PaSR-based soot model for fire applications.
[en] The X-ray absorption coefficient of niobium in the energy range 18.5-19.7 keV around the k-edge is measured using scanning EXAFS synchrotron radiation source. The discrepancies between the measured absorption coefficients and alternative theoretical predictions are discussed. (author)
[en] Using a linked-parametric technique of level-fitting calculations in a multiconfiguration basis, a parametric fine structure (fs) analysis for both even and odd parities of Cr II was achieved. For the first time the fs parameter, magnetic Landé -factor and the percentage of leading eigenvector values for more than one thousand levels are determined and given for these two sets. This study has led us to confirm in the whole the well founded basis of NIST team works but inevitably also to exchange assignments of some levels classified in earlier lists of energy levels and to shift positions of some quartets like for instance. Furthermore we take this opportunity to add our predicted doublet, quartet and sextet locations for missing experimental levels up to 124,000 cm−1.
[en] We study the CDM models with being a function of the time-varying fine structure constant . We give a close look at the constraints on two specific CDM models with one and two model parameters, respectively, based on the cosmological observational measurements along with 313 data points for the time-varying . We find that the model parameters are constrained to be around , which are similar to the results discussed previously but more accurately.
[en] In this paper total mass attenuation coefficient (MAC) for compounds Lanthanum oxide and Lanthanum sulphate, at different X-ray energies were measured. The results compared with theoretical values, agreement found to be good when the incident photon energy is far below and away from the L edge, disagreement is observed near L absorption edges. The mass attenuation co-efficient for a compound is computed using the mixture rule, is given by μ/ρ = Σ ωi (μ/ρ)i. Where ωi is the proportion by weight if the ith element present in the compound and (μ/ρ)i is the mass attenuation coefficient of the ith constituent element of the compound. For a chemical compound ωi can be written as, ωi = ai Ai / Σ(aj Aj). Ai is the atomic weight of the ith element and aj is the number of formula units
[en] Highlights: • The N K-edge NEXAFS spectroscopy of a dipolar molecule DR1P molecule on Graphene was calculated by DFT method. • The feature peaks in experiment were well assigned by the theoretical calculation. • The configuration of the DR1P molecule on Graphene surface was investigated by means of the polarization-dependent NEXAFS spectra.
[en] This work discusses the observation of splitting in the energy levels of prolate nuclei. Similar effects in atomic physics are known as the Zeeman effect, but in nuclear physics the feasibility of such phenomena has not been observed. After introducing a deformation in the commutation relation in three dimensions, we used these commutation relations in X(3) model. After enough derivation, we then evaluate the energy spectrum relation for the considered system, which has resulted in energy splitting. With these observations in the energy splitting we referred to such an effect as the ultra-fine structures in energy levels. At the end some plots have been depicted to illustrate the results. (author)