Navadwīp, India
Navadwīp, India

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Pugatch R.,Institute for Advanced Study | Bhattacharyya D.,Santipur College | Amir A.,Harvard University | Sagi Y.,U.S. National Institute of Standards and Technology | Davidson N.,Weizmann Institute of Science
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

The electromagnetically induced transparency (EIT) spectrum of atoms diffusing in and out of a narrow beam is measured and shown to manifest the two-dimensional δ-function anomaly in a classical setting. In the limit of small-area beams, the EIT line shape is independent of power, and equal to the renormalized local density of states of a free particle Hamiltonian. The measured spectra for different powers and beam sizes collapses to a single universal curve with a characteristic logarithmic Van Hove singularity close to resonance. © 2014 American Physical Society.

Das B.C.,Saha Institute of Nuclear Physics | Bhattacharyya D.,Santipur College | De S.,Saha Institute of Nuclear Physics | De S.,Bhabha Atomic Research Center
Chemical Physics Letters | Year: 2016

We performed an experimental and theoretical study on saturation absorption spectroscopy on Rb87 and Rb85 atoms in D2 transition using a Laguerre-Gaussian (LG) beam with higher orders. We observed narrow line shapes of the Doppler and hyperfine absorption profiles due to the introduction of the LG beam in comparison to the fundamental Gaussian beam. Narrowing of the line shape is dependent on the azimuthal mode index of the LG field. It is observed that the spatially dependent Rabi frequency plays a significant role behind these narrowing phenomenon. © 2015 Elsevier B.V. All rights reserved.

Majumder D.,Santipur College | Majumder D.,Indian Association for The Cultivation of Science | Mandal S.S.,Indian Association for The Cultivation of Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We determine the lowest and higher order collective modes in both spin-conserving and spin-reversed sectors by calculating the energy differences of appropriate linear combinations of different levels of the excitons of the composite fermions and the fully spin-polarized ground states at filling factors ν=1/3, 2/5, 3/7, and 4/9. Apart from providing a detailed study of previously reported modes that have also been observed in the experiments, we predict additional higher energy modes at different filling factors. The lowest and the next higher spin-conserving modes have equal number of "magnetorotons" and the number is the same as the number of filled effective Landau-like levels of composite fermions. The higher energy modes at ν=1/3 merge with the lowest mode at long wavelengths. The spin-conserving modes do not merge at other filling factors. Apart from showing a zero-energy spin-wave mode at zero momentum, thanks to Larmor's theorem, the lowest spin-reversed modes at the ferromagnetic ground states of ν=2/5, 3/7, and 4/9 display one or more "spin rotons" at negative energies, signaling unstable fully polarized ground states at sufficiently small Zeeman energies. The high-energy spin-reversed modes also have spin rotons but at positive energies. The energies of these excitations depend on the finite width of the quantum well as the Coulomb interaction gets screened. We perform a finite thickness correction to the Coulomb interaction by the standard method of local density approximation and use it to calculate the critical energies such as rotons and long- and short-wavelength modes, which are detectable in inelastic light scattering experiments. © 2014 American Physical Society.

Bhattacharyya D.,Santipur College | Ghosh A.,Visva Bharati | Bandyopadhyay A.,Visva Bharati | Saha S.,Saha Institute of Nuclear Physics | De S.,Saha Institute of Nuclear Physics
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2015

We report the observation of electromagnetically induced transparency (EIT) in a six-level Λ-type system in atomic Rb vapor containing both 87Rb and 85Rb. The experimental observation includes five velocity selective optically pumped (VSOP) absorption dips for both 87Rb and 85Rb. The EIT signal appears on the background of one such VSOP absorption dips. The measured EIT linewidth () shows sub-natural ( ) values for both lower and higher values of pump Rabi-frequencies. The density matrix based theoretical model for the six-level system is developed and solved numerically by taking into account the Doppler broadening. A complete analytical solution (non perturbative) for a three level Λ-type system has been obtained and compared with the experimentally observed sub-natural EIT linewidth. The simulated spectra are in good agreement with the experimental findings. © 2015 IOP Publishing Ltd.

Senapati U.,Santipur College | De D.,Vidyasagar University | De B.R.,Vidyasagar University
Indian Journal of Chemistry - Section A Inorganic, Physical, Theoretical and Analytical Chemistry | Year: 2014

A detailed study of Na+ affinities of a series of para-substituted acetophenones and their O-Na+ counterparts has been carried out using density functional theory by B3LYP method using 6-311G(d,p) basis set with complete geometry optimization in the relevant excited state. The gas phase O-Na+ complex formation is exothermic and the local stereochemical disposition of the Na+ is found to be almost the same in each case. The presence of para-substituent causes very little change in the Na+ affinity relative to the unsubstituted acetophenones. Electron releasing p-substituents are seen to increase the affinity, while electron withdrawing p-substituents have an opposite effect. The computed Na+ affinities are correlated with a number of computed system parameters such as the net charge on the Na+ and the carbonyl oxygen of the Na+ complexes and the net charge on the carbonyl oxygen of the free bases as well as the computed hardness of the free bases. The Na+ ion induced shifts are, in general, red shifts for the low-lying excited triplet state. The energetics, structural and electronic properties of the complexes indicate that in the lowest excited triplet state the interaction between the Na+ ion and a carbonyl base is predominantly an ion-dipole attraction and the ioninduced dipole interaction as well rather than a covalent interaction. © 2014, Scientific Publishers. All rights reserved.

Biswas S.,Kalyani University | Kar T.,Utah State University | Sarkar S.,Kalyani University | Sarkar S.,Santipur College | Dey K.,Kalyani University
Journal of Coordination Chemistry | Year: 2012

Some Mn(III) complexes of N,N-(2-hydroxy)propylenebis(acetylacetoneimine) (abbreviated to H 2L 1) and N,N-(2-hydroxy)propylenebis(2- imino-3-oximino)butane (abbreviated to H 2L 2), [Mn(III)(Lig)(X)] (where Lig stands for the dianion of the Schiff-base ligands and X stands for CH 3COO -, Cl -, Br -, I -) were synthesized. The complexes are characterized with the help of elemental analyses, magnetic moments, spectroscopic data (UV-Vis, infrared), and molecular weight determination (measured by Rast's method). The structures of the complexes were obtained using density functional theory (DFT). DFT calculation shows that 1-4 and 8 are trigonal-bipyramidal whereas 5-7 are square-pyramidal. © 2012 Copyright Taylor and Francis Group, LLC.

Sarkar S.,Santipur College | Dey K.,Kalyani University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2010

Some transition and non-transition metal complexes of the hexadentate N4O2 donor Schiff base ligand 1,8-N-bis(3-carboxy) disalicylidene-3,6-diazaoctane-1,8-diamine, abbreviated to H 4fsatrien, have been synthesized. All the 14 metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic (UV-Vis, IR, NMR, ESR) data. The analytical data helped to elucidate the structures of the metal complexes. The Schiff base, H4fsatrien, is found to act as a dibasic hexadentate ligand using N2N2O2 donor set of atoms (leaving the COOH group uncoordinated) leading to an octahedral geometry for the complexes around all the metal ions except VO2+ and UO 2 2+. However, surprisingly the same ligand functions as a neutral hexadentate and neutral tetradentate one towards UO2 2+ and VO2+, respectively. In case of divalent metal complexes they have the general formula [M(H2fsatrien)] (where M stands for Cu, Co, Hg and Zn); for trivalent metal complexes it is [M(H 2fsatrien)]X·nH2O (where M stands for Cr, Mn, Fe, Co and X stands for CH3COO, Cl, NO3, ClO4) and for the complexes of VO2+ and UO2 2+, [M(H 4fsatrien)]Y (where M = VO and Y = SO4; M = UO2 and Y = 2 NO3). The Schiff base ligand and most of the complexes have been screened in vitro to judge their antibacterial (Escherichia coli and Staphylococcus aureus) and antifungal (Aspergillus niger and Pencillium chrysogenum) activities. © 2010 Elsevier B.V.

Islam S.M.,Kalyani University | Singha Roy A.,Kalyani University | Mondal P.,Kalyani University | Mondal S.,Kalyani University | And 3 more authors.
Journal of Applied Polymer Science | Year: 2011

Three polymer-anchored metal complexes (Co, Cu, and Pd) were synthesized and characterized. The catalytic performance of these complexes was tested for the oxidation of olefins and aromatic alcohols. These complexes showed excellent catalytic activity and high selectivity. These complexes selectively gave epoxides and aldehydes from olefins and alcohols, respectively. Individually, the effect of various solvents, oxidants, substrate oxidant molar ratios, temperatures, and catalyst amounts for the oxidation of cyclohexene and benzyl alcohol were studied. Under optimized reaction conditions, 96, 81, and 71% conversions of cyclohexene and 86, 79, and 73% conversions of benzyl alcohol were obtained with Co(II), Cu(II), and Pd(II) catalysts, respectively. The catalytic results reveal that these complexes could be recycled more than five times without much loss in activity. © 2011 Wiley Periodicals, Inc.

PubMed | Santipur College and Saha Institute of Nuclear Physics
Type: Journal Article | Journal: The Journal of chemical physics | Year: 2016

We report here simultaneous experimental observation of Electromagnetically Induced Transparency (EIT) and Electromagnetically Induced Absorption (EIA) in a multi-level V-type system in D

Islam M.,Kalyani University | Mondal P.,Kalyani University | Mukherjee S.,Kalyani University | Mobarak M.,Kalyani University | And 3 more authors.
Journal of Chemical Technology and Biotechnology | Year: 2010

BACKGROUND: Heterogenization of homogeneous catalyst has become an interesting process for the catalytic oxidation of olefins and aromatic alcohol. This may provide a new kind of catalyst that is not only friendly to the environment but also exhibits higher thermal and chemical stabilities. RESULTS: Polymer anchored Schiff-base complexes of iron(III), copper(II) and cobalt(II) have been synthesized and characterized. The catalytic potential of these complexes has been tested for the oxidation of cyclohexene. The effect of varying solvent, oxidant, substrate oxidant molar ratio, temperature and catalyst amount has been studied. Under optimized reaction conditions 91, 88 and 81% conversion of cyclohexene was obtained with Fe(III), Cu(II) and Co(II) catalysts, respectively. Moreover, the oxidation of other substrates, such as styrene, benzylalcohol, toluene and 1-hexene were also efficiently carried out by these catalysts. CONCLUSION: The immobilized complexes showed excellent catalytic activity along with high selectivity for the oxidation of olefins and alcohols. The catalysts can be recycled more than five times without any noticeable loss of catalytic activity. © 2009 Society of Chemical Industry.

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