A trinuclear bright red luminophore containing cyclometallated Ir(III) motifs

The trinuclear complex [{Ir(ppy)(2)}(3)(L(1))(2)](OTf)(3) (1) is a bright red luminophore whereas the monomer [Ir(ppy)(2)L(2)](OTf) (2) exhibits emission in the green region.     

Thermal degradation of alkyl triphenyl phosphonium intercalated montmorillonites

The decomposition mechanism of intercalated montmorillonites at a particular temperature region and the activation energy involved in it are the two important aspects which determines the thermal stability of intercalated montmorillonites. In this study, montmorillonite was intercalated with alkyl (methyl, ethyl, propyl, and dodecyl) triphenyl phosphonium intercalates. Differential thermogravimetric analysis of each intercalated montmorillonites showed different peaks with associated organic loss at different temperature zone. Intercalated montmorillonites were subjected to isothermal kinetic analysis corresponding to selected temperature zone obtained from DTG peaks. Activation energies of organic decomposition process at selected temperature zones were determined. Mass spectral analysis and FTIR were done to understand the decomposition mechanisms and to relate them with the estimated activation energies.     

Cyclometalated Ir–Sn Construct for Cyanosilylation

Two cyclometalated compounds [Ir^IIICl{(2-biphenylene-1,8-naphthyridine-??C,N}(?? ⁵-pentamethylcyclopentadienyl)] (1) and [Ir^IIICl{(2-(2-N-Methyl-pyrrolyl-1,8-naphthyridine-??C,N}(?? ⁵-pentamethylcyclopentadienyl)] (2) containing naphthyridine based ligands have been synthesized in high yield. Insertion of SnCl₂ to a terminal Ir?CCl bond of 1 affords the mixed Ir?CSnCl₃ compound [Ir^IIISnCl₃{(2-biphenylene-1,8-naphthyridine-??C,N}(?? ⁵-pentamethylcyclopentadienyl)] (3). The heterobimetallic compound 3 is shown to be an excellent catalyst for a variety of cyanosilylation reactions. A cooperative mechanism has been proposed which involves the simultaneous activation of aldehyde and cyanide precursor by Sn and unbound naphthyridine nitrogen.     

Propagation of Gaussian beams through parabolic index optical waveguides with random dielectric constant gradient

Abstract

The propagation of gaussian beams through parabolic index optical waveguides having random irregularities in the dielectric constant gradient has been studied. For fundamental mode propagation, the perturbation approach has been employed and an analytic expression for the loss of power from the fundamental mode has been obtained. For an incident gaussian beam with arbitrary width, geometrical optics approximation has been used and an exact analytical expression for the average value of the beamwidth has been derived for a particular random process, namely, the dichotomic Markov process. The fluctuations in the beamwidth have also been calculated.     

Simple theoretical analysis of the Einstein’s photoemission from quantum confined superlattices

In this paper, we study the Einstein’s photoemission from III–V, II–VI, IV–VI and HgTe/CdTe quantum well superlattices (QWSLs) with graded interfaces and quantum well effective mass superlattices in the presence of a quantizing magnetic field on the basis of newly formulated dispersion relations in the respective cases. Besides, the same has been studied from the afore-mentioned quantum dot superlattices and it appears that the photoemission oscillates with increasing carrier degeneracy and quantizing magnetic field in different manners. In addition, the photoemission oscillates with film thickness and increasing photon energy in quantum steps together with the fact that the solution of the Boltzmann transport equation will introduce new physical ideas and new experimental findings under different external conditions. The influence of band structure is apparent from all the figures and we have suggested three applications of the analyses of this paper in the fields of superlattices and microstructures.     

Observation of a universal aggregation mechanism and a possible phase transition in Au sputtered by swift heavy ions

Two exponents delta for the size distribution of n-atom clusters, Y(n) approximately n{-delta}, have been found in Au clusters sputtered from embedded Au nanoparticles under swift heavy ion irradiation. For small clusters, below 12.5 nm in size, delta has been found to be 3/2, which can be rationalized as occurring from a steady state aggregation process with size independent aggregation. For larger clusters, a delta value of 7/2 is suggested, which might come from a dynamical transition to another steady state where aggregation and evaporation rates are size dependent. In the present case, the observed decay exponents do not support any possibility of a thermodynamic liquid-gas-type phase transition taking place, resulting in cluster formation.     

Influence of light waves on the thermoelectric power under large magnetic field in III‐V,ternary and quaternary materials

We study theoretically the influence of light waves on the thermoelectric power under large magnetic field (TPM) for III‐V, ternary and quaternary materials, whose unperturbed energy‐band structures, are defined by the three‐band model of Kane. The solution of the Boltzmann transport equation on the basis of this newly formulated electron dispersion law will introduce new physical ideas and experimental findings in the presence of external photoexcitation. It has been found by taking n‐InAs, n‐InSb, n‐Hg_1‐xCd_xTe and n‐In_1‐xGa_xAs_yP_1‐y lattice matched to InP as examples that the TPM decreases with increase in electron concentration, and increases with increase in intensity and wavelength, respectively in various manners. The strong dependence of the TPM on both light intensity and wavelength reflects the direct signature of light waves that is in direct contrast as compared with the corresponding bulk specimens of the said materials in the absence of external photoexcitation. The rate of change is totally band‐structure dependent and is significantly influenced by the presence of the different energy‐band constants. The well‐known result for the TPM for nondegenerate wide‐gap materials in the absence of light waves has been obtained as a special case of the present analysis under certain limiting conditions and this compatibility is the indirect test of our generalized formalism. Besides, we have also suggested the experimental methods of determining the Einstein relation for the diffusivity:mobility ratio, the Debye screening length and the electronic contribution to the elastic constants for materials having arbitrary dispersion laws.     

On the photoemission from III–V, ternary and quaternary materials: Simplified theory and relative comparison

We study theoretically the electron energy spectrum and the photoemission from III–V, ternary and quaternary materials in the presence of light waves, whose unperturbed energy band structures are defined by the three-band model of Kane. The band gap of semiconductors increases as a consequence of incident light waves and we have suggested two new experimental methods of determining the band gap of semiconductors in the presence of photoexcitations. The solution of the Boltzmann transport equation on the basis of this newly formulated electron dispersion law will introduce new physical ideas and experimental findings in the presence of external photoexcitation. It has been found taking n-InAs, n-InSb, n-Hg_1−xCd_xTe and n-In_1−xGa_xAs_yP_1−y lattice matched to InP, as examples that the photoemission increases with the increase in electron concentration and decreases in increasing intensity, wavelength and alloy composition, respectively, in various manners. The numerical values of the photoemission in the presence of light waves is less than that of the same for unperturbed three- and two-band models of Kane together with parabolic energy bands for all types of external variables. The strong dependence of the photoemission on the light intensity reflects the direct signature of light waves on the dispersion relation of the conduction electrons, which is in contrast when compared with the corresponding bulk specimens for the unperturbed band models. The rate of change is totally band structure dependent and is significantly influenced by the presence of the different energy band constants. The well-known result of the photoemission from non-degenerate wide gap materials has been obtained as a special case of the present analysis under certain limiting conditions and this compatibility is the indirect test of our generalized formalism. Besides, we have suggested six important applications of our results in this context.     

Coupling of two parallel multimode parabolic index waveguides: An exact analysis in the weakly guiding approximation

A model analysis of a guiding structure consisting of two parallel multimode parabolic-index waveguides in the weakly guiding approximation has been presented. Such structures are expected to play an important role as directional couplers in data bus systems, etc. The modes thus obtained have been used to study the power exchange between the two waveguides and a simple analytical expression has been obtained for the coupling length in a case of practical importance.