Optical Characterization of Donor Doped Ternary Alloy Ga1-xNxAs and GaN-Ga1-xNxAs MQW by Using Infrared Fourier Transform Spectroscopy

In this work polarized infrared Fourier transform spectroscopy is employed to study the electronic and optical properties of doped Ga_1-xN_xAs ternary alloy and GaN-Ga_1-xN_xAs MQW. We have analyzed the far infrared spectra of GaN-GaNAs MQW by using a simple macroscopic theory base on effective medium approximation model. The dispersion curve of coupled LO phonon- plasmon modes were calculated from the polarized infrared reflectivity data. The GaNAs layer shows two-mode behavior in the infrared spectral range, a GaAs-like and a GaN-like sublattices. We detect the transverse optic phonon of GaN sublattice around 475 cm^-1. The origin of the sharp feature in p-polarization reflectivity about 300 cm^-1 as well as the dip at LO phonon frequency of GaAs sublattice are due to Brewster mode. The Brewster mode is couple strongly to plasmon mode. Attenuated total reflection spectroscopy has been used to excite and investigate surface plasmon and surface polariton.     

NaBrO3/NaHSO4 · H2O as a Versatile Reagent System for the Oxidation of Benzylic Alcohols and Aldehydes

The oxidation of benzylic alcohols and aldehydes by NaBrO₃ is efficiently promoted in the presence of NaHSO₄ · H₂O. All reactions were performed under mild and completely heterogeneous conditions in good to high yields.     

Note: Deperturbation of the ν3 band of BeD2

High rotational levels of the 001 (Σ(u)) state of BeD(2) are perturbed by the nearby 03(3)0 (Φ(u)) state. Deperturbation analysis results in an experimental value for the vibrational energy of the 030 level.     

The quantum compass chain in a transverse magnetic field

We study the magnetic behaviors of a spin-1/2 quantum compass chain (QCC) in a transverse magnetic field, by means of the analytical spinless fermion approach and numerical Lanczos method. In the absence of the magnetic field, the phase diagram is divided into four gapped regions. To determine what happens by applying a transverse magnetic field, using the spinless fermion approach, critical fields are obtained as a function of exchanges. Our analytical results show, the field-induced effects depend on in which one of the four regions the system is. In two regions of the phase diagram, the Ising-type phase transition happens in a finite field. In another region, we have identified two quantum phase transitions (QPT)s in the ground state magnetic phase diagram. These quantum phase transitions belong to the universality class of the commensurate-incommensurate phase transition. We also present a detailed numerical analysis of the low energy spectrum and the ground state magnetic phase diagram. In particular, we show that the intermediate state (h _c1 < h < h _c2) is gapful, describing the spin-flop phase.     

Optimization of a quantum-dot semiconductor optical amplifier (QD-SOA) design using the genetic algorithm

Optical and Quantum Electronics - We review a novel approach to the light scattering by small layered particles in the electrostatic limit when the particle is considered to be in the uniform...     

Directed C−H Halogenation Reactions Catalysed by PdII Supported on Polymers under Batch and Continuous Flow Conditions

A new generation of N-heterocyclic carbene palladium(II) complexes containing vinyl groups in different positions in the backbone of the N-heterocycle have been developed. The fully characterised monomers were copolymerised with divinylbenzene to fabricate robust polymer supported NHC-Pd^II complexes and these polymers were applied as heterogeneous catalysts in directed C−H halogenation of arenes with a pyridine-type directing group. The catalysts demonstrated medium-high catalytic activity with up to 90 % conversion and 100 % selectivity in chlorination. They are heterogeneous and recyclable (at least six times) with no significant leaching of palladium in batch mode catalysis. The best catalyst was also applied under continuous flow conditions where it disclosed an exceptional activity (90 % conversion) and 100 % selectivity for the mono-halogenated product for at least six days, with no leaching of palladium, no loss of activity and an ability to maintain the original oxidation state of Pd^II.     

Neutronic calculations for CANDU thorium systems using Monte Carlo techniques

In this paper, we have investigated the prospects of exploiting the rich world thorium reserves using Canada Deuterium Uranium （CANDU） reactors. The analysis is performed using the Monte Carlo MCNP code in order to understand how much time the reactor is in criticality conduction. Four different fuel compositions have been selected for analysis. We have obtained the infinite multiplication factor, k∞, under full power operation of the reactor over 8 years. The neutronic flux distribution in the full core reactor has already been investigated.     

Ab initio calculations on low-lying electronic states of PdH

Potential energy curves for the low-lying electronic states of PdH have been calculated using the MRCI method with scalar relativistic and spin-orbit corrections, and all electronic states correlating to the 4d¹⁰ (¹S), 4d⁹ 5s¹ (³D), 4d⁹ 5s¹ (¹D) and 4d⁸ 5s² (³F) states of Pd were included. Potential energy curves for the individual Ω states have been obtained, and the experimentally observed spectra of both PdH and PdD isotopologues have been assigned appropriately based on the ab initio results. Einstein A coefficients were calculated for other possible transitions from the low-lying electronic states to the X²Σ⁺ ground state. Diagonal and off-diagonal matrix elements of the spin-orbit Hamiltonian were calculated for all vibrational levels of the X²Σ⁺, 1²Δ, 1²Π, 2²Σ⁺ and 3²Σ⁺ states, and it was found from the eigenvectors that the vibrational wavefunctions of the 1²Δ_3/2 and 1²Π_3/2 states are mixed significantly in both PdH and PdD isotopologues.     

Modelling the effect of slave laser gain and frequency comb spacing on the selective amplification of injection locked semiconductor lasers

A rate equation model was used to model the optical filtering properties of injection locked semiconductor lasers. Numerical and experimental results are presented which show the changes in the comb rejection ratio (CRR) of an injection locked single mode laser due to the gain of the slave laser. It was found that there is an optimal slave laser current at which the CRR of the slave laser is largest, and good qualitative agreement is present between the model and experiment. The model was also used to predict the effects of the target carrier’s position on the optical comb. It was found that locking the slave laser to the outer comb lines gave slightly worse CRRs than when locking to the central lines. It is also shown that for comb frequency spacings close to the relaxation oscillation frequency of the slave laser, the obtainable CRR is significantly decreased.     

Magnetic properties of the spin S = 1/2 Heisenberg chain with hexamer modulation of exchange

We consider the spin-1/2 Heisenberg chain with alternating spin exchange in the presence of additional modulation of exchange on odd bonds with period 3. We study the ground state magnetic phase diagram of this hexamer spin chain in the limit of very strong antiferromagnetic (AF) exchange on odd bonds using the numerical Lanczos method and bosonization approach. In the limit of strong magnetic field commensurate with the dominating AF exchange, the model is mapped onto an effective XXZ Heisenberg chain in the presence of uniform and spatially modulated fields, which is studied using the standard continuum-limit bosonization approach. In the absence of additional hexamer modulation, the model undergoes a quantum phase transition from a gapped phase into the only one gapless Lüttinger liquid (LL) phase by increasing the magnetic field. In the presence of hexamer modulation, two new gapped phases are identified in the ground state at magnetization equal to [Formula: see text] and [Formula: see text] of the saturation value. These phases reveal themselves also in the magnetization curve as plateaus at corresponding values of magnetization. As a result, the magnetic phase diagram of the hexamer chain shows seven different quantum phases, four gapped and three gapless, and the system is characterized by six critical fields which mark quantum phase transitions between the ordered gapped and the LL gapless phases.