• JAIVIR SINGH

      Articles written in Pramana – Journal of Physics

    • Fragment production in 16O+80Br reaction within dynamical microscopic theory

      Rajeev K Puri Jaivir Singh Suneel Kumar

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      We analyze the formation of fragments in O—Br reaction at different incident energies between E/A=50 MeV and 200 MeV. This study is carried out within the quantum molecular dynamics (QMD) model coupled with recently advanced simulated annealing clusterization algorithm (SACA). For comparison, we also use the conventional minimum spanning tree (MST) method. Our detailed study shows that the SACA can detect the final stable fragment configuration as early as 60 fin/c which is marked by a dip in the heaviest fragment. On the other hand, the MST method needs several hundred fm/c to identify the final stable distribution. A comparison of the charge distribution with experimental data shows that the SACA is able to reproduce the data very nicely whereas (as reported earlier) the MST method fails to break the spectator matter into intermediate mass fragments. Furthermore, our results with SACA method indicate the onset of multi-fragmentation around 75 MeV/A which is again in good agreement with experimental findings.

    • Enhanced Raman gain coefficients (under steady-state and transient regimes) of semiconductor magnetoplasmas

      JAIVIR SINGH SUNITA DAHIYA MANJEET SINGH

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      Assuming the origination of stimulated Raman scattering (SRS) in Raman susceptibility, we obtain expressions for Raman gain coefficients (under steady-state and transient regimes) of semiconductor magnetoplasmas under various geometrical configurations. The threshold value of excitation intensity and most favourable value of pulse duration (above which transient Raman gain vanishes) are estimated. For numerical calculations, we consider n-InSb crystal at 77K temperature as a Raman-active medium exposed to a frequencydoubled pulsed CO$_2$ laser. The variation of Raman gain coefficients on doping concentration, magnetostatic field and its inclination, scattering angle and pump pulse duration have been explored in detail with an aim to determinesuitable values of these controllable parameters to enhance Raman gain coefficients at lower threshold intensities and to establish the suitability of semiconductor magnetoplasmas as hosts for compression of scattered pulses and fabrication of efficient Raman amplifiers and oscillators based on Raman nonlinearities.

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