• S K Ghosh

      Articles written in Pramana – Journal of Physics

    • Three-dimensional wake potential in a streaming dusty plasma

      M Salahuddin M K Islam A K Banerjee M Salimullah S K Ghosh

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      The oscillatory wake potential for a slowly moving or static test dust particulate in a finite temperature, collisionless and unmagnetized dusty plasma with a continuous flow of ions and dust particles has been studied. The collective resonant interaction of the moving test particle with the low-frequency and low-phase-velocity dust-acoustic mode is the origin of the periodic attractive force between the like polarity particulates along and perpendicular to the streaming ions and dust grains resulting into dust-Coulomb crystal formation. This wake potential can explain the three-dimensional dust-Coulomb crystal formation in the laboratory conditions.

    • Scattering length density profile of Ni film under controlled corrosion: A study in neutron reflectometry

      Surendra Singh A K Poswal S K Ghosh Saibal Basu

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      We report the density depth profile of an as-deposited Ni film and density profile for the same film after controlled electrochemical corrosion by chloride ions, measured by unpolarized neutron reflectometry. The neutron reflectometry measurement of the film after corrosion shows density degradation along the thickness of the film. The density profile as a function of depth, maps the growth of pitting and void networks due to corrosion. The profile after corrosion shows an interesting peaking nature.

    • Photophysical and laser characteristics of pyrromethene 567 dye: Experimental and theoretical studies

      K K Jagtap D K Maity A K Ray K Dasgupta S K Ghosh

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      Narrow-band laser performance of alcohol solutions of pyrromethene 567 (PM567) and rhodamine 6G (RH6G) dye was investigated using a home-made GIG- configured dye laser, excited by the second-harmonic radiation (at 532 nm) of a pulsed Nd:YAG laser. Higher laser efficiency was observed with PM567 dye ($\sim 23%$ peak) in comparison to the commonly used RH6G dye (16.5%), in spite of much lower fluorescence quantum efficiency of the PM567 (0.83) vis-à-vis RH6G (0.98) dye solutions in ethanol. First principle-based electronic structure calculations were performed on PM567 dye in the ground ($S_{0}$) and excited states ($S_{1}$) using density functional theory to elucidate the structure and photophysical properties of the dye.

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