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111.
Ruma?Karmakar Chirantan?Roy?Choudhury Samiran?MitraEmail author Lutz?Dahlenburg 《Structural chemistry》2005,16(6):611-616
One novel copper(II) complex [Cu(L)(4,4′-bipy)](ClO4) (1), (where L: tridentate Schiff base derived from salicylaldehyde and L-serine) has been synthesised and characterised by spectroscopic and electrochemical studies. The single-crystal structure
of the complex was determined. The crystal structure features the presence of [Cu(L)(4,4′-bipy)]+ cations and ClO4− anions aggregated by hydrogen bonding. Here, 4,4′-bipyridine functions as a monodentate ligand, which appears to be an unusual
phenomenon. 相似文献
112.
Chaudhuri P Karmakar S Dasgupta C Krishnamurthy HR Sood AK 《Physical review letters》2005,95(24):248301
The phase diagram of a polydisperse hard-sphere system is examined by numerical minimization of a discretized form of the Ramakrishnan-Yussouff free-energy functional. Crystalline and glassy local minima of the free energy are located and the phase diagram in the density-polydispersity plane is mapped out by comparing the free energies of different local minima. The crystalline phase disappears and the glass becomes the equilibrium phase beyond a "terminal" value of the polydispersity. A crystal-to-glass transition is also observed as the density is increased at high polydispersity. The phase diagram obtained in our study is qualitatively similar to that of hard spheres in a quenched random potential. 相似文献
113.
Kinetics of the extraction of V(IV) from acidic sulfate medium by Cyanex 301 dissolved in kerosene has been investigated using a constant interfacial area stirred cell with laminar flow (Lewis cell). Reaction orders with respect to different concentration terms, rate constant, activation energy, entropy change in activation, and the enthalpy change in activation have been measured at a phase circulation speed of 3 Hz. The rate equation at 293 K is F (kmol/m2s) = 10?7.02 (1 + 0.025[V(IV)]?1)?1 (1 + 398[H+])?1 (1 + 0.10 [HA]o?1)?1 (1 + 3.16 [SO42?]). Based on the experimental results, the mechanism of extraction has been proposed. 相似文献
114.
Subir Kumar Sarkar Anupam Karmakar Ashis Kumar De 《Czechoslovak Journal of Physics》2001,51(3):249-256
Small-signal ac transport of degenerate one-dimensional hot electrons in quantum wires of GaAs and In0.53Ga0.47As is studied for lattice temperatures of 77 K and 300 K. The carrier energy loss via polar optic phonons and momentum losses via polar optic phonons, acoustic phonons and ionized impurities are included in the calculations. Alloy disorder scattering in momentum loss is additionally incorporated for (In,Ga)As. The consideration of nonequilibrium optical phonons or hot phonons is found to enhance the 3dB cut-off frequency (f3dB) considerably, where the ac mobility falls to 0.707 of its low frequency value. f3dB is generally higher for (In,Ga)As quantum wire than for GaAs. 相似文献
115.
116.
Tirtha Som Basudeb Karmakar 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(2):640-646
Dichroic Sm3+: Au-antimony glass nanocomposites are synthesized in a new reducing glass (dielectric) matrix (mol%) K2O–B2O3–Sb2O3 (KBS) by a single-step melt-quench technique involving selective thermochemical reduction. X-ray diffraction (XRD) and selected area electron diffraction (SAED) results indicate that Au0 nanoparticles are grown along the (2 0 0) plane direction. The transmission electron microscopic (TEM) image reveals the elliptical Au0 nanoparticles having major axis range 12–17 nm. Dichroic behavior is due to elliptical shape of Au0 nanoparticles of aspect ratio ~1.2. Au0 NPs of concentration of 0.03 wt% (4.1 × 1018 atoms/cm3) drastically enhances the intensity (~7-folds) of electric dipole 4G5/2 → 6H9/2 red transition (636 nm) of Sm3+ ions and then attenuates with further increase in Au0 concentration. The magnetic dipole 4G5/2 → 6H5/2 green (566 nm) and 4G5/2 → 6H7/2 orange (602 nm) transitions remain almost unaffected by presence of nano Au0. Local field enhancement (LFE) induced by Au0 SPR and energy transfer (ET) from fluorescent Au0 → Sm3+ ions are found to be responsible for the enhancement while reverse ET from Sm3+ → Au0 and optical re-absorption due to Au0 SPR for attenuation. 相似文献
117.
Nd3+-doped precursor glass in the K2O–SiO2–Y2O3–Al2O3 (KSYA) system was prepared by the melt-quench technique. The transparent Y3Al5O12 (YAG) glass–ceramics were derived from this glass by a controlled crystallization process at 750 °C for 5–100 h. The formation of YAG crystal phase, size and morphology with progress of heat-treatment was examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Fourier transformed infrared reflectance spectroscopy (FT-IRRS). The crystallite sizes obtained from XRD are found to increase with heat-treatment time and vary in the range 25–40 nm. The measured photoluminescence spectra have exhibited emission transitions of 4F3/2 → 4IJ (J = 9/2, 11/2 and 13/2) from Nd3+ ions upon excitation at 829 nm. It is observed that the photoluminescence intensity and excited state lifetime of Nd3+ ions decrease with increase in heat-treatment time. The present study indicates that the incorporation of Nd3+ ions into YAG crystal lattice enhance the fluorescence performance of the glass–ceramic nanocomposites. 相似文献
118.
119.
Qiao B Zepf M Borghesi M Dromey B Geissler M Karmakar A Gibbon P 《Physical review letters》2010,105(15):155002
A new ion radiation-pressure acceleration regime, the "leaky light sail," is proposed which uses sub-skin-depth nanometer foils irradiated by circularly polarized laser pulses. In the regime, the foil is partially transparent, continuously leaking electrons out along with the transmitted laser field. This feature can be exploited by a multispecies nanofoil configuration to stabilize the acceleration of the light ion component, supplementing the latter with an excess of electrons leaked from those associated with the heavy ions to avoid Coulomb explosion. It is shown by 2D particle-in-cell simulations that a monoenergetic proton beam with energy 18 MeV is produced by circularly polarized lasers at intensities of just 101? W/cm2. 100 MeV proton beams are obtained by increasing the intensities to 2 × 102? W/cm2. 相似文献
120.
Subhasis Mallick Subala Mondal Biplab K. Bera Parnajyoti Karmakar Sankar C. Moi Alak K. Ghosh 《Transition Metal Chemistry》2010,35(4):469-475
The kinetics of the interaction between thiourea and the title complex has been studied spectrophotometrically in aqueous
medium as a function of nucleophile concentration, temperature and pH at constant ionic strength. The reaction is a two-step
process in which the first step is ligand dependent, but the second step is ligand independent and is assigned to ring closure.
The rate and activation parameters, conductivity studies and IR data were used to deduce a plausible mechanism. 相似文献