Articles written in Pramana – Journal of Physics

    • Inelastic surface vibrations versus energy-dependent nucleus–nucleus potential in sub-barrier fusion dynamics of $^{6}_{3}$ Li + $^{144} -{62}$Sm system


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      Limitations of the static Woods–Saxon potential and the applicability of the energy dependent Woods–Saxon potential (EDWSP) model within the framework of one-dimensional Wong formula to explore the sub-barrier fusion data are highlighted. The inelastic surface excitations of the fusing nuclei are found to be dominating in the enhancement of sub-barrier fusion excitation function data and the effects of such dominant vibrational states are exploited through the coupled channel calculations obtained by using the code CCFULL. It is worth mentioning here that the influence of multiphonon vibrational states of the reactants can be simulated by introducing the energy dependence in the nucleus–nucleus potential.

    • Analytical evaluation of cesium emission lines using laser-induced breakdown spectroscopy


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      A laser-induced breakdown spectroscopy-based method has been successfully developed to quantify cesium (Cs) in solution using spectroscopically pure graphite planchets as a sample support. As Cs is a line-poor system, only five usable Cs atomic emission lines could be found and characterised by employing high-resolution system. The calibration curves of these emission lines were constructed under optimised experimental conditions. The analytical properties of these calibration curves were evaluated based on the usable dynamic range, $R^{2}$ of fitting, root mean square error cross-validation and limit of detection (LOD). The dynamic ranges of these five lines were found to be in correlation with the energy level involved in the transition. An LOD of 4 ppm was obtained using Cs(I) 852.11-nm line, which corresponds to 0.16 $\mu$g of Cs on the planchet. Based on the cross-validation approach, the best accuracy and precision ($\sim$6%) were obtained for 852.11 nm in >3000 ppm solutions, and the same is $\sim$8% for 672.33 nm and 697.33 nm in high concentrated solution of Cs.

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


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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.

    • Hot carrier effects on Brillouin susceptibilities of semiconductor magnetoplasmas


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      An analytical investigation is made of hot carrier effects on real and imaginary parts of Brillouin susceptibility (Re, Im (χB)) of semiconductor magnetoplasmas. Coupled mode approach is used to obtain expressions for Re, Im (χB) Numerical calculations are made for the n-InSb crystal–CO$_2$ laser system. Efforts are made to obtain enhanced values of Re, Im(χB) and change of their sign by an appropriate selection of external magnetic field (B$_0$) and doping concentration (n$_0$). The hot carrier effects of intense laser radiation modify the momentum transfer collision frequency of carriers and consequently, the nonlinearity of the medium, which in turn (i) further enhances Re, Im(χB), (ii) shifts the enhanced Re, Im (χB) towards smaller values of B$_0$ and (iii) widens the range of B$_0$at which change of sign of Re, Im(χB)occurs. The change of sign of enhanced Re, Im(χB)of semiconductor magnetoplasmas validates the possibility of the chosen Brillouin medium as a potential candidate material for the fabrication of stimulated Brillouin scattering-dependent widely tunable and efficient optoelectronic devices such as optical switches and frequency converters.

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