Showing papers by "Indian Association for the Cultivation of Science published in 1991"
TL;DR: In this paper, electrical conductivity, Hall mobility, thermoelectric power and optical properties were studied for indium-doped zinc oxide films produced by the magnetron sputtering technique.
145 citations
TL;DR: It is shown that both the main and the satellite peaks from UCC-LRT for the one valence problems are core-valence extensive owing to the hermitized nature of the underlying operator to be diagonalized, and hence the energy differences are fully extensive.
Abstract: In this paper we have discussed in detail the aspects of separability of the energy differences obtained from coupled cluster based “direct” methods such as the open-shell Coupled Cluster (CC) theory and the Coupled Cluster based Linear Response Theory (CC-LRT). It has been emphasized that, unlike the state energiesper se, the energy differences have a semi-local character in that, in the asymptotic limit of non-interacting subsystemsA, B, C, etc., they are separable as ΔE
A
, ΔE
B
, ΔE
A
+ ΔE
B
, etc. depending on the subsystems excited. We classify the direct many-body methods into two categories: core-extensive and core-valence extensive. In the former, we only implicitly subtract the ground state energy computed in a size-extensive manner; the energy differences are not chosen to be valence-extensive (separable) in the semi-local sense. The core-valence extensive theories, on the other hand, are fully extensive — i.e., with respect to both core and valence interactions, and hence display the semi-local separability. Generic structures of the wave-operators for core-extensive and core-valence extensive theories are discussed. CC-LRT is shown to be core-extensive after a transcription to an equivalent wave-operator based form. The emergence of valence disconnected diagrams for two and higher valence problems are indicated. The open-shell CC theory is shown to be core-valence extensive and hence fully connected. For one valence problems, the CC theory and the CC-LRT are shown to be equivalent. The equations for the cluster amplitudes in the Bloch equation are quadratic, admitting of multiple solutions. It is shown that the cluster amplitudes for the main peaks, in principle obtainable as a series inV from the zeroth order roots of the model space, are connected, and hence the energy differences are fully extensive. It is remarkable that the satellite energies obtained from the alternative solutions of the CC equations are not valence-extensive, indicating the necessity of a formal power series structure inV of the cluster amplitudes for the valence-extensivity. The alternative solutions are not obtainable as a power series inV. The CC-LRT is shown to have an effective hamiltonian structure respecting “downward reducibility”. A unitary version of CC-LRT (UCC-LRT) is proposed, which satisfy both upward and downward reducibility. UCC-LRT is shown to lead to the recent propagator theory known as the Algebraic Diagrammatic Construction. It is shown that both the main and the satellite peaks from UCC-LRT for the one valence problems are core-valence extensive owing to the hermitized nature of the underlying operator to be diagonalized.
100 citations
TL;DR: In this paper, the effects of post-deposition heat treatment in vacuum and hydrogen atmosphere on the above properties were studied to derive meaningful information on the scattering mechanisms in ZnO:Al films.
76 citations
TL;DR: In this paper, a tentative explanation of the first phase formation is proposed, and the activation energy of grain boundary diffusion as determined from contact electrical resistance measurements is about 0.34 eV.
59 citations
TL;DR: In this article, stable state and time-resolved fluorometric investigations of the excited state proton transfer reactions of carbazole and 2-naphthylamine in the presence of β-cyclodextrin are reported.
Abstract: Steady state and time-resolved fluorometric investigations of the excited state proton transfer reactions of carbazole and 2-naphthylamine in the presence of β-cyclodextrin are reported in this paper. The results, together with earlier reports, reveal that the prototropic reaction depends not only on the microenvironment of the molecule, which is imposed by cyclodextrin, but also on the nature of the molecule itself. Thus, in comparison with the bare chromophore, the deprotonation rate of the cyclodextrin inclusion complex is enhanced when the guest molecule is carbazole, whereas it is decreased for guests like naphthylamine or naphthols.
52 citations
TL;DR: The Michael reaction of several β-dicarbonyl compounds, such as methyl vinyl ketone, acrolein and methyl acrylate as acceptors, was carried out in this paper without any solvent.
46 citations
TL;DR: In this paper, cyclometallated platinum(IV) complexes of the type [Pt(RL)Cl3] incorporating azobenzene (R = H) or 4-methylazobenzenes with an SCH2Ph (L = L1) or an S(O)CH2Ph substituent in an ortho position are described.
42 citations
TL;DR: Effect of urea on the fluorescence properties of p-toluidino naphthalene sulphonate bound to triton-X and sodium dodecyl sulfate micelles has been studied and the results are interpreted in terms of the model that urea displaces water molecules from the micellar interface and the consequent desolvation leads to removal of TNS molecules from
38 citations
TL;DR: The first numerical applications of the size-extensive quasi-Hilbert- and quasi-Fock-space coupled-cluster theories to the ground and the first excited 1,3 Σ states of the molecule LiH were reported in this article.
37 citations
TL;DR: Optical properties of Cd1−xZnxTe films (0.1 < × < 0.7) were strudied as a function of incident photon energy in this article.
36 citations
TL;DR: In this paper, the effect of grain growth of zinc oxide films deposited by using a reactive DC magnetron sputtering technique was studied as a function of annealing temperature, and the results were correlated with the observed electrical and optical studies.
TL;DR: In this article, the optical properties of copper-indium-diselenide films in the wavelength range of 500-3000 nm were analyzed in the light of existing theories and indicated a Burstein-Moss shift in these films.
TL;DR: In this paper, the viability of the Metropolis simulated-annealing method (MSAM) in the optimization of molecular geometry is tested and the ability of MSAM to seek out the global energy minimum on a potential energy hypersurface with multiple minima is demonstrated.
TL;DR: In this article, a series of neutral chelate compounds [Pd 2 L(AB) 2 ] has been obtained by reacting the precursor with sodium salts of acetylacetone, ethylacetoacetate, N-methylsalicylaldimine (HAB), and N,N′-dimethyldithiocarbamic acid (Hab).
TL;DR: The effect of the Ps-formation channel on elastic scattering is found to be pronounced at low incident energies, and this effect is not negligible even up to 50 eV.
Abstract: Positron-lithium scattering has been investigated using the three-state (Li(2{ital s}), Li(2{ital p}), and Ps(1{ital s})) close-coupling approximation. Calculations have also been carried out by using the static, coupled static, and Born approximations. Elastic (2{ital s}-2{ital s}), excitation (2{ital s}-2{ital p}), and Ps-formation cross sections are reported up to an incident energy of 100 eV. The effect of the Ps-formation channel on elastic scattering is found to be pronounced at low incident energies, and this effect is not negligible even up to 50 eV. The positronium formation cross section is reduced appreciably in the energy region 1.0--20.0 eV when the 2{ital p} state is included in the expansion scheme.
TL;DR: Zinc borohydride in 1,2-dimethoxvethane reduces α-substituted conjugated nitroalkenes to the corresponding oximes and non-α-substantituted ones to their corresponding nitronalkanes in excellent yields as mentioned in this paper.
TL;DR: In this paper, an efficient methodology using zinc borohydride under sonification for the reduction of carboxylic esters to alcohols in presence of N,N-dimethylaniline and selective reduction of an aliphatic ester over an aromatic one without N, N-Ndimethyl-dimethyliline is described.
TL;DR: In this paper, a depth profiling technique using secondary ion mass spectrometry was used to study the diffusion of elements in amorphous silicon solar cells, and the thickness of the SnO 2 layer was varied to check the indium diffusion into the p and i layers.
TL;DR: The fluorescence excitation spectrum of jet-cooled 9,10-dihydrophenanthrene is reported in this paper, showing a prominent progression of a low-frequency vibration which is assigned to inter-ring torsional motion.
TL;DR: In this paper, the inner-sphere electron transfer reaction of transcyclohexane-1,2-diamine-NNN'N'-tetraacetic acid (H 4 cydta) and 2,2'-bipyridyl (bpy) was investigated in the acid range [H + ]=1.00×10 −5 −3.
Abstract: The kinetics of the reactions of manganese(III) complexes of trans-cyclohexane-1,2-diamine-NNN'N'-tetraacetic acid (H 4 cydta) and 2,2'-bipyridyl (bpy) have been investigated in the acid range [H + ]=1.00×10 −5 −3.16×10 −3 M and [H + ]=0.10−1.00 M, respectively, at different temperatures and at a constant ionic strength. Both the molecular and mono-anionic forms of ascorbic acid have been found to be reactive in the experimental acid ranges. The monoanionic species has been found to be more reactive than the molecular form. Attempts have been made to correlate the kinetic results in terms of the Marcus relationship for outer-sphere electron transfer reaction. Differences between the calculated rates (k 0.s ) and experimental rates (k) by approximately four and seven orders of magnitude (k 0.s k) suggest an innersphere pathway for the reaction of Mn(cydta)(H 2 O) − . Inner-sphere reaction is also believed to be operative for the other reaction. The activation parameters have been evaluated and compared with other reported systems
TL;DR: In this article, a detailed analysis of emission and absorption spectra of 2,6-diphenyl pyridine (DPP), m -terphenyl (MTP), and 2, 6-luitidine (LTD) in different solvents was performed.
TL;DR: In this paper, a cone angle is defined for an alkyl group (R), which is proposed as a measure of the steric effect exerted by the group, and correspondences between θR and the two existing steric parameters (Taft's Es scale and Dubois' E′s scale) have been established.
TL;DR: Etude de la stabilite du bipolaron de Froblich dans la limite du couplage fort en deux et trois dimensions en utilisant la methode de l'integrale de passage de Feynman-Haken and le formalisme de Landau-Pekar.
Abstract: The stability of the Fr\"ohlich bipolaron in the strong-coupling limit is studied in both two and three dimensions using the Feynman-Haken path-integral method and the Landau-Pekar formalism. The ground-state energy, the effective mass, and the size of the bipolaron are obtained, and its stability criteria are predicted. The role of Coulomb correlation is also studied.
TL;DR: In this article, light-induced changes in the photoconductivity and defect density have been compared in deuterated and hydrogenated amorphous silicon, and the results are explained in terms of two kinds of recombination center which are photocreated at different rates.
Abstract: Light-induced changes in the photoconductivity and defect density have been compared in deuterated and hydrogenated amorphous silicon. There is no significant difference between the as-deposited properties of the two materials; however, the photoconductivity degrades more slowly but anneals more rapidly in material prepared using the heavier isotope. In hydrogenated material, the average photocarrier recombination cross-section of the defects increases with light soaking but the opposite occurs in deuterated material. These results are explained in terms of two kinds of recombination centre which are photocreated at different rates. The variation in the degradation and annealing behaviour of photoconductivity with deposition temperature implies subtle structural differences between the two materials which, for the first time, gives rise to the possibility of controlling photodegradation in amorphous silicon.
TL;DR: It has been shown that, with a suitable choice of the distorting potential, the boundary condition may be satisfied with a proper account of the intermediate continuum states and leads to the same transition amplitude as may be derived using the Vainshtein-Presnyakov-Sobelman approximation.
Abstract: Positronium formation into ground and n=2 levels has been studied in collisions of positrons with atomic hydrogen in the framework of an approximation called the boundary-corrected continuum-intermediate-state (BCCIS) approximation in the energy range of 0.08--2 keV. The conventional continuum-intermediate-state approximation does not satisfy the correct boundary condition. It has been shown that, with a suitable choice of the distorting potential, the boundary condition may be satisfied with a proper account of the intermediate continuum states. It has also been shown that the BCCIS approximation leads to the same transition amplitude as may be derived using the Vainshtein-Presnyakov-Sobelman approximation. The results obtained here are found to be in good agreement when compared with other theoretical results.
TL;DR: In this article, the parity-allowed direct two-photon transitions within the 4f 7 configuration of Gd 3+ ion in a centrosymmetric Cl − environment are presented.
TL;DR: In this article, the tetrazolate complex [PdL(N4C-p-OMeC6H4) (1) was characterized from its IR and 1H NMR spectra, and X-ray crystal structure.
TL;DR: In this article, the free energy of transfer of CTAB from the aqueous to the polymer phase has been calculated, considering water and polymer to be in separate phases, and spectral results indicate dye aggregation (stacking) on the flexible polymer chain.
Abstract: The interactions of the polyelectrolyte carboxymethylcellulose (sodium salt) with salts, dyes and surfactants have been studied by viscometry, conductometry, spectrophotometry and membrane potential measurements. The compact conformation of the polyelectrolyte has been realized in all the environments. The average radius of gyration, s, and the intrinsic viscosity, [η], decline with increasing concentration of the additives. This and the narrow pseudoternary single-phase zones for both the carboxymethylcellulose (sodium salt)/CTAB (cetyltrimethylammonium bromide)1 / Triton X-100 (α-alkylphenyl-ω-hydroxypoly(oxyethylene))/water and the carboxymethylcellulose (sodium salt)/CTAB/Tween 20 (poly(oxyethylene)sorbitan monolaurate)/water system suggest instability of the polymer in presence of the additives. The spectral results indicate dye aggregation (stacking) on the flexible polymer chain. The binding of CTAB with the polyelectrolyte is Langmuirian in absence of KCl and strongly co-operative in its presence. Thermodynamic parameters have been evaluated in the light of both Langmuir and Scatchard equations. Considering water and polymer to be in separate phases, the free energy of transfer of CTAB from the aqueous to the polymer phase has been calculated.
TL;DR: In this paper, the effect of post deposition heat treatments in air and in a hydrogen atmosphere on the optical properties of aluminium doped zinc oxide (ZnO : Al) films was studied in the spectral range of 300-1400 nm.
TL;DR: In this paper, the Simulated Annealing (SAN) method was applied to the ground and the singlet 1S2S states of a few members of the He-isoelectronic sequence.