Energy levels, oscillator strengths and lifetimes in Ar V

We have calculated the excitation energies, oscillator strengths and transition probabilities for electric-dipole-allowed and intercombination transitions among the 46 LS levels belonging to the configurations 3s ²3p ², 3s3p ³, 3s ²3p3d, 3p ⁴, 3s ²3p4s, 3s ²3p4p, 3s3p ²(² S)4s, 3s3p ²(² P)4s, 3s3p ²(⁴ P)4s, 3s3p ²(² D)4s, 3s ²3p4d and 3s ²3p4f of Si-like Argon. These states are represented by extensive Configuration-Interaction (CI) wavefunctions obtained using the CIV3 computer code of Hibbert. From our transition probabilities we have also calculated the radiative lifetimes of singlet and triplet states of Ar V. Our results are compared with other available theoretical calculations and experimental data. To assess the importance of relativistic effects on our calculated values, we have also carried out calculations in the intermediate-coupling scheme using the Breit-Pauli Hamiltonian. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made so that the energy splittings are as close as possible to the experimentally compiled energy values of the National Institute for standards and Technology (NIST). The energy splitting of 85 fine-structure levels, the oscillator strengths and transition probabilities for electric-dipole-allowed and intercombination transitions and the lifetimes of some fine-structure levels are presented and compared with available experimental and other theoretical values. In this calculation, we also predict new data for several fine-structure levels where no other theoretical and experimental results are available.     

Simulations of atomic level stresses in systems of buried Ge /Si islands.

Stress distribution in laterally ordered arrays of coherent Ge islands on Si(001) buried in Si cap layers is examined using atomistic simulations. The obtained hydrostatic stress dependence on the spacer layer thickness shows a nearly linear inverse dependence, unlike the commonly used inverse cubic dependence derived in the framework of an isolated embedded force dipole source model. Additionally, the hydrostatic stress on the spacer surface is found to scale more closely with the area of the island rather than its volume as implicit in the use of the force dipole model.     

Multicomponent Approach to Hydantoins and Thiohydantoins Involving a Deep Eutectic Solvent

We report an efficient synthetic strategy to diverse hydantoins and thiohydantoins involving a three‐component reaction with the aid of deep eutectic solvent. Here, N,N′‐dimethyl urea and N,N′‐dimethyl thiourea play a dual role as reactant and reaction medium along with l ‐(+)‐tartaric acid. The three‐component reaction provides an easy access to 5‐amino‐1,3‐dialkyl‐substituted hydantoins and thiohydantoins in good yields.     

Energy and photoinduced electron transfer in a wheel-shaped artificial photosynthetic antenna-reaction center complex

Functional mimics of a photosynthetic antenna-reaction center complex comprising five bis(phenylethynyl)anthracene antenna moieties and a porphyrin-fullerene dyad organized by a central hexaphenylbenzene core have been prepared and studied spectroscopically. The molecules successfully integrate singlet-singlet energy transfer and photoinduced electron transfer. Energy transfer from the five antennas to the porphyrin occurs on the picosecond time scale with a quantum yield of 1.0. Comparisons with model compounds and theory suggest that the F?rster mechanism plays a major role in the extremely rapid energy transfer, which occurs at rates comparable to those seen in some photosynthetic antenna systems. A through-bond, electron exchange mechanism also contributes. The porphyrin first excited singlet state donates an electron to the attached fullerene to yield a P(*+)-C(60)(*-) charge-separated state, which has a lifetime of several nanoseconds. The quantum yield of charge separation based on light absorbed by the antenna chromophores is 80% for the free base molecule and 96% for the zinc analogue.     

Fuzzy Application to the Analytic Hierarchy Process for Robot Selection

The problem of Robot Selection is of great relevance in the present times of automation. Traditionally such problems were addressed using conventional techniques of Multi Criteria Decision Making such as The Analytic Hierarchy Process (AHP) and The Multi Attribute Utility Theory (MAUT). This paper proposes a methodology for solving common Robot Selection problems using a modification of the conventional AHP by incorporating ‘Fuzzy Linguistic Variables’ in place of numbers. The methodology encapsulates creation of Fuzzy Interface for conversion of input and output variables into suitable linguistic variables. Further, employing the fuzzification process by assigning the linguistic variables to numerical values of the membership functions and formulating suitable decision rules, the procedure culminates into the defuzzification process for converting fuzzy output into crisp value and obtaining the result in the form of Fuzzy Score. The proposed model is explained using a numerical example. The paper also presents a validation of the proposed methodology over real world problems and provides directions for future research towards the end.Additional support was provided by the National Science Foundation.     

Magnetic ordering versus lattice distortion in very narrow bands

A simple criterion for antiferromagnetic ordering versus lattice distortion in very narrow band materials is obtained. The model describing these narrow band materials contains the Hubbard Hamiltonian, short ranged interatomic Coulomb and exchange interactions, and the electron-phonon interaction.     

A pressure-shear plate impact experiment for investigating transient friction

A pressure-shear plate impact experiment is introduced to study time-resolved friction at interfaces subjected to high sliding speeds under relatively high normal pressures. The conditions of slip at the interface are varied by changing the surface roughness of the impacting plates and by varying the applied normal to shear stress ratio. The configuration offers the simplicity of allowing the interpretation of the experimental data by using the frame-work of one-dimensional plane wave analysis. The interfacial material pairs investigated in the present study are comprised of a wear-resistant grade of tungsten carbide and either an AISI 4340 steel or a Ti-6AI-4V alloy. The experimental results indicate that the coefficient of friction increases with the increase in surface roughness of the tungsten-carbide plates and with cumulative slip at the interface.     

X-ray K-absorption fine structure study of CuxZn1-xFe2O4 (x = 0.2, 0.4, 0.6 and 0.8)

For Cu_xZn_1-xFe₂O₄ spinel ferrites (x = 0.2, 0.4, 0.6 and 0.8), EXAFS of Cu and Fe K-absorption edges have been studied employing LSS theory. With change in copper content, in the spinel system, the basic dependence of cation distribution on degree of inversion has been reported by plotting variation of bond distance “d” with EXAFS parameter ‘α’. This is further substantiated by plotting chemical shifts (ΔE) with EXAFS parameter ‘α’. The necessity of the determination of final state wavefunction for the knowledge of distribution of charge is stressed.     

Computer simulations of the role of group V molecular reactions at steps during molecular beam epitaxial growth of III-V semiconductors

The Configuration Dependent Reactive Incorporation (CDRI) model is used to study the growth of III-V semiconductors by MBE. In particular, the role of the dissociative reaction of the group V molecular species from the physisorbed precursor state is studied. The model allows for the reaction to occur at pairs of vacant group V sites which are intra- or interplanar nearest neighbors on the group V sublattice. Within this model, it is shown that a relatively small number of depositions at steps can play an important role in determining the smoothness of the growth front and the effective migration length of the group III species. Conditions under which these depositions are likely to be less influential are also discussed.     

Gauss law constraints on Debye-Hückel screening

The half-lives are calculated for the β ⁻ decay process for nuclei in the mass range ∼65–75 relevant for the core of a massive star at the late burning stage of stellar evolution and the collapse that leads to supernova explosion. These half-lives and rates are calculated by expressing the β ⁻ Gamow-Teller decay strengths in terms of smoothed bivariate strength densities. These strength densities are constructed in the framework of spectral averaging theory for two-body nuclear Hamiltonian in a large nuclear shell model space. The method has a natural extension to electron captures as well as weak interaction rates for r and rp-processes.