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      Articles written in Pramana – Journal of Physics

    • A comparative study of the density of defect states in bulk samples and thin films of glassy Se$_{90}$Sb$_{10}$

      KUMAR ANJANI DWIVEDI PRABHAT K SHUKLA R K KUMAR A

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      The present paper reports the comparative study of density of defect states (DOS) between bulk samples and thin films of glassy Se$_{90}$Sb$_{10}$. These glasses have been prepared by the quenching technique. Thin films of these glasses have been prepared by vacuum evaporation technique. Space-charge-limited conduction (SCLC) has been measured at different temperatures.The density of localized states near Fermi level is calculated by fitting the data to the theory of SCLC for the case of uniform distribution of localized states for bulk as well as for thin films. A comparison has been made between the density of states calculated in these two cases.

    • Shock wave propagation in soda lime glass using optical shadowgraphy

      PRASAD Y B S R BARNWAL S NAIK P A YADAV Y PATIDAR R KAMATH M P UPADHYAY A BAGCHI S KUMAR A JOSHI A S GUPTA P D

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      Propagation of shock waves in soda lime glass, which is a transparent material, has been studied using the optical shadowgraphy technique. The time-resolved shock velocity information has been obtained (1) in single shot, using the chirped pulse shadowgraphy technique, with a temporal resolution of tens of picoseconds and (2) in multiple shots, using conventional snapshot approach, with a second harmonic probe pulse. Transient shock velocities of $(5–7) \times 10^{6}$ cm/s have been obtained. The scaling of the shock velocity with intensity in the $2 \times 10^{13}–10^{14}$ W/cm$^2$ range has been obtained. The shock velocity is observed to scale with laser intensity as $I^{0.38}$. The present experiments also show the presence of ionization tracks, generated probably due to X-ray hotspots from small-scale filamentation instabilities. The results and various issues involved in these experiments are discussed

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